Click on "Install Server".
Wait a few minutes for the server to deploy. Once ready, it will show a "Started" state.
In the chat, type @ followed by the MCP server name and your instructions, e.g., "@Serial MCP Server List serial ports and connect to /dev/ttyUSB0 at 115200 baud."
That's it! The server will respond to your query, and you can continue using it as needed.
Here is a step-by-step guide with screenshots.
A stateful serial port Model Context Protocol (MCP) server for developer tooling and AI agents. Works out of the box with Claude Code, VS Code with Copilot, and any MCP-compatible runtime. Communicates over stdio and uses pyserial for cross-platform serial on macOS, Windows, and Linux.
Example: Let Claude Code list available serial ports, connect to your microcontroller, reset it via DTR, and read the boot banner from your hardware.
Video walkthrough — connecting to a serial device, sending commands, reading responses, and creating plugins.
If you’ve ever copy-pasted commands into screen or minicom, guessed baud rates, toggled DTR to kick a bootloader, and re-run the same test sequence 20 times — this is for you.
You have a serial device. You want an AI agent to talk to it — open a port, send commands, read responses, debug protocols. This server makes that possible.
It gives any MCP-compatible agent a full set of serial tools: listing ports, opening connections, reading, writing, line-oriented I/O, control line manipulation — plus protocol specs and device plugins, so the agent can reason about higher-level device behavior instead of just raw bytes.
The agent calls these tools, gets structured JSON back, and reasons about what to do next — without you manually typing commands into a terminal for every step.
What agents can do with it:
Develop and debug — connect to your device, send commands, read responses, and diagnose issues conversationally (boot banners, prompts, error codes).
Iterate on new firmware — attach a protocol spec so the agent understands your command set, boot modes, and output format as they evolve.
Automate test flows — reset device via DTR, wait for prompt, run a command sequence, validate output.
Explore unknown devices — probe command sets, discover prompts, infer message formats.
Build serial automation — long-running test rigs, manufacturing bring-up, CI hardware smoke tests.
Related MCP server: UART MCP Server
Embedded engineers — faster iteration on serial protocols, conversational debugging, automated test sequences
Hobbyists and makers — interact with serial devices without writing boilerplate; let the agent help reverse-engineer simple protocols
QA and test engineers — build repeatable serial test suites with plugin tools
Support and field engineers — diagnose serial device issues interactively without specialized tooling
Researchers — automate data collection from serial devices, explore device capabilities systematically
pip install serial-mcp-server
# Register the MCP server with Claude Code
claude mcp add serial -- serial_mcpThen in Claude Code, try:
"List available serial ports and connect to the one on /dev/ttyUSB0 at 115200 baud."
Once connected, the agent has full serial capabilities:
List ports to find available serial devices
Open and close connections with configurable baud rate, parity, stop bits, and encoding
Read and write data in text, hex, or base64 format
Line-oriented I/O — readline and read-until-delimiter for text protocols
Control lines — set or pulse DTR and RTS for hardware reset and boot mode entry
Flush input and output buffers
Attach protocol specs to understand device-specific commands and data formats
Use plugins for high-level device operations instead of raw reads/writes
Create specs and plugins for new devices so future sessions start "knowing" your protocol
PTY mirroring — attach screen, minicom, or custom scripts to the same serial session the agent is using
The agent can coordinate multi-step flows automatically — e.g., toggle reset, wait for prompt, send init sequence, stream output.
At a high level:
Raw Serial → Protocol Spec → Plugin
You can start with raw serial tools, then move up the stack as your device protocol becomes understood and repeatable.
# Editable install from repo root
pip install -e .
# Or with uv
uv pip install -e .MCP is a protocol — this server works with any MCP-compatible client. Below are setup instructions for the most common ones.
# Standard setup
claude mcp add serial -- serial_mcp
# Or run as a module
claude mcp add serial -- python -m serial_mcp_server
# Enable all plugins
claude mcp add serial -e SERIAL_MCP_PLUGINS=all -- serial_mcp
# Enable specific plugins only
claude mcp add serial -e SERIAL_MCP_PLUGINS=mydevice,ota -- serial_mcp
# Debug logging
claude mcp add serial -e SERIAL_MCP_LOG_LEVEL=DEBUG -- serial_mcpAdd to your project's .vscode/mcp.json (or create it):
{
"servers": {
"serial": {
"type": "stdio",
"command": "serial_mcp",
"args": [],
"env": {
"SERIAL_MCP_PLUGINS": "all"
}
}
}
}Adjust env to match your needs — set SERIAL_MCP_PLUGINS to specific plugin names, or add SERIAL_MCP_MIRROR for PTY mirroring.
Add to your project's .cursor/mcp.json (or create it). Cursor does not support dots in tool names, so SERIAL_MCP_TOOL_SEPARATOR must be set to _:
{
"mcpServers": {
"serial": {
"command": "serial_mcp",
"args": [],
"env": {
"SERIAL_MCP_PLUGINS": "all",
"SERIAL_MCP_TOOL_SEPARATOR": "_"
}
}
}
}Variable | Default | Description |
|
| Maximum simultaneous open serial connections. |
| disabled | Plugin policy: |
|
| PTY mirror mode: |
|
| Base path for PTY symlinks. Connections get numbered: |
|
| Python log level ( |
| enabled | JSONL tracing of every tool call. Set to |
| disabled | Include write |
|
| Max payload chars before truncation (only applies when |
|
| Character used to separate tool name segments. Set to |
Category | Tools |
Serial Core |
|
Introspection |
|
Protocol Specs |
|
Tracing |
|
Plugins |
|
Specs are markdown files that describe a serial device's protocol — connection settings, message format, commands, and multi-step flows. They live in .serial_mcp/specs/ and teach the agent what the byte stream means.
Without a spec, the agent can still open a port and exchange data. With a spec, it knows what commands to send, what responses to expect, and what the data means.
You can create specs by telling the agent about your device — paste a datasheet, describe the protocol, or just let it explore and document what it finds. The agent generates the spec file, registers it, and references it in future sessions. You can also write specs by hand.
Plugins add device-specific shortcut tools to the server. Instead of the agent composing raw read/write sequences, a plugin provides high-level operations like mydevice.read_temp or ota.upload_firmware.
The agent can also generate Python plugins (with your approval). It explores a device, writes a plugin based on what it learns, and future sessions get shortcut tools — no manual coding required.
To enable plugins:
# Enable all plugins
claude mcp add serial -e SERIAL_MCP_PLUGINS=all -- serial_mcp
# Enable specific plugins only
claude mcp add serial -e SERIAL_MCP_PLUGINS=mydevice,ota -- serial_mcpEditing an already-loaded plugin only requires serial.plugin.reload — no restart needed.
Every tool call is traced to .serial_mcp/traces/trace.jsonl and an in-memory ring buffer (last 2000 events). Tracing is on by default — set SERIAL_MCP_TRACE=0 to disable.
Two events per tool call:
{"ts":"2025-01-01T00:00:00.000Z","event":"tool_call_start","tool":"serial.read","args":{"connection_id":"s1"},"connection_id":"s1"}
{"ts":"2025-01-01T00:00:00.050Z","event":"tool_call_end","tool":"serial.read","ok":true,"error_code":null,"duration_ms":50,"connection_id":"s1"}connection_id is extracted from args when present
Write data is stripped from traced args by default (enable with SERIAL_MCP_TRACE_PAYLOADS=1)
Use serial.trace.status to check config and event count, and serial.trace.tail to retrieve recent events — no need to read the file directly.
When the MCP server owns a serial port, most OSes prevent any other process from opening it. PTY mirroring creates a virtual clone port that external tools (screen, minicom, logic analyzers, custom scripts) can connect to simultaneously.
# Enable read-only mirror
claude mcp add serial \
-e SERIAL_MCP_MIRROR=ro \
-- serial_mcp
# After opening a connection, the response includes the mirror path:
# { "mirror": { "pty_path": "/dev/ttys004", "link": "/tmp/serial-mcp0", "mode": "ro" } }
# In another terminal:
screen /tmp/serial-mcp0 115200Mode | Behavior |
| No mirror (default). Only the MCP server can access the port. |
| External tools see all serial data but cannot write to the device. |
| External tools can both see data and write to the device. |
Platform: macOS and Linux only. On Windows, setting SERIAL_MCP_MIRROR to ro/rw logs a warning and is silently ignored.
You can test the server interactively using the MCP Inspector — no Claude or other agent needed:
npx @modelcontextprotocol/inspector python -m serial_mcp_serverOpen the URL with the auth token from the terminal output. The Inspector gives you a web UI to call any tool and see responses in real time.
Single-client only. The server handles one MCP session at a time (stdio transport). Multi-client transports (HTTP/SSE) may be added later.
Exclusive access. Without PTY mirroring, the MCP server must own the serial port exclusively.
This server connects an AI agent to real hardware. That's the point — and it means the stakes are higher than pure-software tools.
Plugins execute arbitrary code. When plugins are enabled, the agent can create and run Python code on your machine with full server privileges. Review agent-generated plugins before loading them. Use SERIAL_MCP_PLUGINS=name1,name2 to allow only specific plugins rather than all.
Writes affect real devices. A bad command sent to a serial device can trigger unintended behavior, disrupt other connected systems, or cause hardware damage (e.g., wiping flash, entering bootloader mode, triggering actuators). Consider what the agent can reach.
Use tool approval deliberately. When your MCP client prompts you to approve a tool call, consider whether you want to allow it once or always. "Always allow" is convenient but means the agent can repeat that action without further confirmation.
This software is provided as-is under the MIT License. You are responsible for what the agent does with your hardware.
This project is licensed under the MIT License — see LICENSE for details.
This project is built on top of the excellent pyserial library for cross-platform serial communication in Python.
Close a serial port connection and release the port.
| Name | Required | Description | Default |
|---|---|---|---|
| connection_id | Yes | The connection_id from serial.open. |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations provided, and the description only states 'close and release' without detailing behavior on double-close, error handling, or blocking characteristics.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Single sentence, front-loaded action, no extraneous words. Efficient and to the point.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Despite simplicity, missing details on idempotency, error states, and whether it flushes buffers. The description is inadequate for an agent to handle edge cases.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema covers 100% of the single parameter with a clear description. The tool description adds no additional meaning beyond the schema.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
Description clearly specifies the action (close) and resource (serial port connection), and distinguishes from sibling tools like serial.open and serial.read/write.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
No explicit guidance on when to use this tool (e.g., after serial.open, before closing). The context of siblings implies usage but lacks direct instruction.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
List all open serial connections with their status, port, configuration, and timestamps. Useful for recovering connection IDs after context loss.
| Name | Required | Description | Default |
|---|---|---|---|
No parameters | |||
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full burden. It clearly describes the read-only nature ('List') and the return contents. Since this is a straightforward listing operation, the description adequately discloses behavior without contradictions.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Two concise sentences with no wasted words. The first sentence front-loads the purpose and return fields; the second adds a practical use case. Ideal length for this simple tool.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given no parameters, no output schema, and no annotations, the description is sufficiently complete. It states what it returns and one key use case. It could hint at prerequisites (e.g., requires an open connection), but it's clear that it lists only open connections.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
The tool has zero parameters and 100% schema description coverage. According to guidelines, baseline is 4 for zero parameters. The description appropriately does not add parameter info as none exist.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states it lists all open serial connections with specific fields (status, port, configuration, timestamps). The verb 'List' and resource scope are precise, and it distinguishes from siblings like 'serial.connection_status' which likely focus on a single connection.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The tool explicitly mentions a specific use case: 'Useful for recovering connection IDs after context loss.' However, it does not provide explicit when-not-to-use guidance or alternatives, but the given use case is clear and helpful.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Check whether a serial connection is still open and return its configuration.
| Name | Required | Description | Default |
|---|---|---|---|
| connection_id | Yes | The connection_id from serial.open. |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description must carry the behavioral burden. It indicates a read-only check (no side effects) but does not specify behavior on invalid connection_id or details of the returned configuration.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Single sentence, front-loaded with the core purpose, no wasted words.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given no output schema, the description should hint at return structure. It says 'return its configuration' but lacks specifics. The presence of many sibling tools provides some context but does not compensate for missing return detail.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema coverage is 100% as the only parameter has a description. The tool description adds minimal extra meaning beyond the schema.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the tool's action: check connection status and return configuration. It distinguishes from siblings like serial.open, serial.close, and serial.connections.list.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
No explicit guidance on when to use this tool versus alternatives such as serial.connections.list. The description implies usage after opening a connection but does not provide when-not-to-use or alternative scenarios.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Flush serial port buffers (discard pending input/output data).
| Name | Required | Description | Default |
|---|---|---|---|
| connection_id | Yes | ||
| what | No | Which buffer to flush: input, output, or both (default both). | both |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description must fully disclose behavior. It correctly states that pending data is discarded, which is a critical side effect. However, it does not explicitly mention irreversibility or potential loss, nor does it detail any other behavioral traits (e.g., effect on buffers, permissions, or error states).
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is a single, front-loaded sentence with no filler. It efficiently conveys the core purpose and effect.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the simplicity of the tool (flush with two parameters) and no output schema, the description is adequate but not thorough. It lacks context about the 'connection_id' parameter (e.g., how to obtain it) and any return behavior, which would be helpful for a complete understanding.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 50% (only 'what' is described). The tool description does not add any meaning to the 'connection_id' parameter, which is undocumented in the schema. The 'what' parameter is already well-described in the schema. Thus, the description fails to compensate for the missing parameter documentation.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the action ('flush') and the resource ('serial port buffers'), and explains the effect ('discard pending input/output data'). It is specific and easily distinguishes from sibling tools like read, write, or close.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
No guidance is provided on when to use this tool versus alternatives. There is no mention of typical scenarios, prerequisites, or exclusions. The usage context is left entirely implicit.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
List available serial ports on the system.
| Name | Required | Description | Default |
|---|---|---|---|
No parameters | |||
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Without annotations, the description carries the full burden of behavioral disclosure. It correctly indicates this is a read-only listing operation, but it does not disclose any additional behaviors such as error conditions, permissions required, or what 'available' means in terms of port discovery.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is a single sentence with no unnecessary words. It is front-loaded and efficient, fitting the tool's simplicity.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the tool's low complexity (zero parameters, no output schema), the description is minimal but adequate. However, it lacks details about the return format or potential errors, leaving some ambiguity for the AI agent. A perfect score would require slightly more context about what the list contains.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
The tool has zero parameters, and the input schema covers 100% of nothing. The description adds the semantic meaning that the tool lists 'available' ports, which is appropriate for a parameterless tool. According to guidelines, baseline is 4 for zero parameters, and the description meets that.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the action ('List') and the resource ('available serial ports'). It is a specific verb+resource combination that distinguishes it from sibling tools like serial.open or serial.read, which operate on connections rather than enumerating ports.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description provides no guidance on when to use this tool versus alternatives. It does not mention any context, prerequisites, or situations where listing ports is appropriate, nor does it suggest alternatives for other types of enumeration.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Open a serial port connection. Returns a connection_id for use with other serial tools. The port stays open across tool calls until serial.close is called or the server exits. Defaults are 115200 baud, 8N1, \r\n line terminator — the most common settings. If you don't know the correct settings, check for a protocol spec with serial.spec.list or ask the user. Wrong baud rate is the most common cause of garbled data. After opening: 1) Use serial.spec.list to check for a matching protocol spec. If a match is found, attach it with serial.spec.attach. 2) Use serial.plugin.list to check for a plugin that matches the device. If a matching plugin is loaded, its tools are available to use directly. 3) Do a serial.read to check for any buffered data — many devices send a boot banner, prompt, or status message on connection.
| Name | Required | Description | Default |
|---|---|---|---|
| port | Yes | Serial port path (e.g. /dev/ttyUSB0, COM3). | |
| baudrate | No | Baud rate (default 115200). Common values: 9600, 19200, 38400, 57600, 115200. | |
| bytesize | No | Data bits (default 8). | |
| parity | No | Parity: N(one), E(ven), O(dd), M(ark), S(pace). Default N. | N |
| stopbits | No | Stop bits (default 1). | |
| timeout_ms | No | Read timeout in milliseconds (default 200). | |
| write_timeout_ms | No | Write timeout in milliseconds (default 200). | |
| exclusive | No | Request exclusive access (platform-dependent, ignored if unsupported). | |
| encoding | No | Default text encoding for this connection (default utf-8). | utf-8 |
| newline | No | Default line terminator for readline and append_newline (default \r\n). | \r\n |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations provided, so description carries full burden. Discloses that port stays open, defaults, common cause of garbled data (wrong baud rate), and expected post-open actions. Lacks mention of permission issues but is otherwise thorough.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Well-structured: starts with purpose, then persistence, defaults, then a numbered list of steps. Each sentence adds value, though slightly long. Front-loaded with core information.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given 10 parameters, 100% schema coverage, no output schema, and no annotations, the description is remarkably complete. Covers lifecycle, defaults, common errors, and post-open workflow. Leaves little ambiguity for an agent.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema coverage is 100%, so baseline 3. Description adds value by contextualizing defaults (e.g., 'most common settings'), explaining common pitfalls (wrong baud rate), and clarifying the purpose of parameters like newline and encoding.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
Clearly states 'Open a serial port connection' and explains it returns a connection_id for use with other serial tools. Distinguishes from siblings by noting the port stays open across calls until serial.close.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
Provides explicit guidance on when to use (check settings if unsure, defaults given) and a step-by-step process after opening. Does not explicitly mention when not to use, but context from siblings implies it's the first step.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
List loaded plugins with their tool names and metadata. Each plugin may include a 'meta' dict with matching hints like device_name_contains or description — use these to determine which plugin fits the connected device. Also returns whether plugins are enabled and the current policy. Plugins require SERIAL_MCP_PLUGINS env var — set to 'all' for all or 'name1,name2' to allow specific plugins. If disabled, tell the user to set this variable when adding the MCP server.
| Name | Required | Description | Default |
|---|---|---|---|
No parameters | |||
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the burden. It discloses the env var requirement, that the tool returns metadata including hints, enabled status, and policy. It implies a read-only operation without side effects, though not explicitly stated.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is three sentences, each earning its place. The first sentence states the main purpose, the second adds crucial detail about metadata, and the third gives actionable usage guidance. No waste.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a listing tool with no parameters and no output schema, the description adequately explains what is returned (tool names, metadata, enabled status, policy) and the prerequisite env var. It is complete for an agent to understand and use this tool.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
The input schema has zero parameters, so no parameter explanation is needed. The baseline is 4, and the description adds context about what the tool returns and its dependencies, but not about parameters since there are none.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the tool lists loaded plugins with tool names and metadata. It distinguishes from sibling tools like serial.plugin.load or serial.plugin.reload because it is a list operation, not a modification or template.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description provides explicit guidance on requiring the SERIAL_MCP_PLUGINS env var and what to tell the user if plugins are disabled. While it doesn't explicitly name alternatives, the context of sibling tools implies when to use other plugin management tools.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Load a new plugin from a file or directory path. Requires SERIAL_MCP_PLUGINS env var to be set.
| Name | Required | Description | Default |
|---|---|---|---|
| path | Yes | Path to a .py file or directory containing __init__.py. |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations provided, so description must cover behavioral traits. It states the env var requirement but omits effects like duplicate load behavior, errors on invalid path, or required permissions.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Two short sentences, efficient and front-loaded with the action. However, omits necessary details that could have been added without expanding much.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a load operation with one parameter and no output schema, description should clarify success/failure indicators, idempotency, and side effects. It is incomplete.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema has 100% coverage for the single parameter 'path' with a clear description. The tool description adds no new semantic information beyond the schema.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
Description clearly states 'Load a new plugin from a file or directory path', specifying the verb (load), resource (plugin), and method. It differentiates from sibling tools like list, reload, template.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
Only mentions the prerequisite environment variable SERIAL_MCP_PLUGINS. No guidance on when to use this tool vs alternatives (e.g., reload), nor exclusions or typical use cases.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Hot-reload a plugin by name. Re-imports the module and refreshes tools. Requires SERIAL_MCP_PLUGINS env var to be set.
| Name | Required | Description | Default |
|---|---|---|---|
| name | Yes | Name of the loaded plugin to reload. |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations provided, so the description carries full burden. It transparently describes the action (reload, re-import, refresh tools) which implies a safe operation. It does not elaborate on error states or side effects.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is two sentences: first states the action and effect, second provides a prerequisite. No irrelevant information, front-loaded with the core action.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the tool has one parameter, no output schema, and no annotations, the description covers the essential: what it does and a prerequisite. It lacks error handling notes (e.g., if plugin not found) but is mostly complete.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
The single parameter 'name' is described in the schema as 'Name of the loaded plugin to reload.' The description adds the env var requirement but does not clarify what constitutes a valid 'name' (e.g., file name or plugin ID). Given 100% schema coverage, baseline 3 is appropriate.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the tool hot-reloads a plugin by name, specifying it re-imports the module and refreshes tools. This distinguishes it from sibling tools like serial.plugin.load (initial load) and serial.plugin.list (listing).
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description provides a clear prerequisite: requires SERIAL_MCP_PLUGINS env var to be set. It does not explicitly state when not to use the tool or mention alternatives, but the context is adequate for a simple tool.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Return a Python plugin template. Use this when creating a new plugin. Optionally pre-fill with a device name. Save the result to .serial_mcp/plugins/.py, fill in the tools and handlers, then load with serial.plugin.load.
| Name | Required | Description | Default |
|---|---|---|---|
| device_name | No | Device name to pre-fill in the template. |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description bears full responsibility for behavioral disclosure. It states the tool returns a template, implying a non-destructive read-only operation, but does not explicitly guarantee no side effects or state changes. The optional device name pre-fill is noted, and the lack of warnings for destructive behavior is acceptable given the template generation nature.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description consists of three sentences, each with a distinct purpose: stating the tool's function, its usage scenario, and the follow-up workflow. It is front-loaded with the key action and efficiently provides necessary context without redundant words.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a simple tool with one optional parameter and no output schema, the description covers its purpose, usage context, and follow-up steps. It mentions the sibling tool for loading and the file path. However, it does not explicitly state the return type (e.g., a string with Python code), which would slightly enhance completeness.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema coverage is 100% for the single parameter, so the baseline is 3. The description mentions 'Optionally pre-fill with a device name,' which aligns with the schema description but adds no additional constraints or formatting details. The parameter meaning is adequately conveyed without extra enrichment.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states 'Return a Python plugin template' and distinguishes from siblings like serial.plugin.load by specifying 'Use this when creating a new plugin.' The verb 'Return' and resource 'Python plugin template' are specific and actionable.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description explicitly says 'Use this when creating a new plugin' and provides a step-by-step workflow: save to file, fill in tools/handlers, then load with serial.plugin.load. This gives clear guidance on when to use and how to proceed, effectively distinguishing from sibling tools.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Pulse the DTR line: sets low, waits duration_ms, then sets high. Commonly used to reset microcontrollers (e.g. Arduino, ESP32). Check the protocol spec or ask the user before pulsing — effect is device-specific.
| Name | Required | Description | Default |
|---|---|---|---|
| connection_id | Yes | ||
| duration_ms | No | Pulse duration in milliseconds (default 100). |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations provided, the description effectively discloses the behavioral details: it sets DTR low, waits duration_ms, then sets high. It also notes the effect is device-specific, which adds honesty about variability. This goes beyond minimal transparency.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is extremely concise with two sentences, front-loading the action and then adding important context. Every word adds value without redundancy.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the tool's simplicity (2 parameters, no output schema), the description covers the main purpose, use case, and a caution. It is sufficiently complete for an agent to understand and invoke the tool, though it could mention potential side effects or return behavior.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
The description reinforces the purpose of duration_ms by saying 'waits duration_ms', but the schema already provides a description for that parameter. The connection_id parameter lacks description in both the schema and the tool description, so the tool description adds no new semantic value for the parameters.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states 'Pulse the DTR line' with a specific verb and resource, and describes the sequence (sets low, waits, sets high). It distinguishes itself from siblings like serial.set_dtr and serial.pulse_rts by focusing on pulsing DTR rather than constant set or RTS pulse.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description gives a common use case (resetting microcontrollers) and a caution to check the protocol or ask the user before pulsing. However, it does not explicitly mention when to use this tool over alternatives (e.g., serial.pulse_rts) or when not to use it.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Pulse the RTS line: sets low, waits duration_ms, then sets high. Some devices use RTS to enter bootloader mode. Check the protocol spec or ask the user before pulsing — effect is device-specific.
| Name | Required | Description | Default |
|---|---|---|---|
| connection_id | Yes | ||
| duration_ms | No | Pulse duration in milliseconds (default 100). |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Describes the sequence of actions (low, wait, high) and warns about device-specific side effects. With no annotations, this is sufficient for understanding the tool's impact.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Two sentences, front-loaded with action, then context and warning. No wasted words.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the simple tool (2 params, no output schema), the description covers behavior, purpose, and caution. Minor gap: no mention of return value or error behavior, but acceptable.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Description adds meaning to duration_ms by explaining its role in the pulse sequence. However, connection_id is not elaborated. Schema coverage is 50% but description partially compensates.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
Clearly states it pulses the RTS line (sets low, waits, sets high). Mentions specific use case (bootloader mode) and distinguishes from siblings like serial.set_rts and serial.pulse_dtr.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
Explicitly advises to check protocol spec or ask user before pulsing due to device-specific effects. Provides caution but does not name alternative tools.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Read up to nbytes from a serial port. Returns immediately with whatever data is available within the timeout. Use serial.readline or serial.read_until for line-oriented reads.
| Name | Required | Description | Default |
|---|---|---|---|
| connection_id | Yes | ||
| nbytes | No | Maximum bytes to read (default 256). | |
| timeout_ms | No | Override read timeout for this call only (milliseconds). | |
| as | No | Output format: text (decoded string), hex, or base64. Default text. | text |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries full burden. It discloses that the read is non-blocking ('Returns immediately') and bounded by a timeout and nbytes. However, it does not specify error behavior (e.g., on timeout or invalid connection) or the exact return format, which are important for a read operation.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is concise at two sentences, with the purpose front-loaded and the alternative guidance efficiently placed. Every sentence adds value without redundancy.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given four parameters and no annotations or output schema, the description lacks important context: it does not mention the return type (string in text/hex/base64), the required open connection, or error scenarios. This leaves significant gaps for an agent to use the tool correctly.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema coverage is 75%, but the description only reiterates 'nbytes' from the schema ('Read up to nbytes'). It adds no explanation for connection_id, timeout_ms, or the 'as' format parameter, leaving the agent to rely solely on schema descriptions for these.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the verb 'Read' and the resource 'serial port', specifying behavior 'Returns immediately with whatever data is available within the timeout.' It distinguishes from sibling tools serial.readline and serial.read_until by naming them explicitly for line-oriented reads.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description provides explicit guidance to use alternative tools for line-oriented reads ('Use serial.readline or serial.read_until for line-oriented reads.'), which helps in selecting the right tool. However, it does not explicitly state when not to use this tool (e.g., when line-based reading is needed).
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Read a line from the serial port (reads until the newline character is received or max_bytes is reached). Uses the connection's newline setting by default.
| Name | Required | Description | Default |
|---|---|---|---|
| connection_id | Yes | ||
| timeout_ms | No | Override read timeout (milliseconds). | |
| max_bytes | No | Maximum bytes to read (default 4096). | |
| newline | No | Override line terminator (defaults to connection newline). | |
| as | No | Output format (default text). | text |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description discloses that reading stops at newline or max_bytes and uses connection's newline setting. However, it omits details on blocking, timeout, error handling, or return format beyond the schema.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Two sentences, no redundant information. Every sentence serves a clear purpose: stating the action and highlighting the default newline behavior.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given 5 parameters and no output schema, the description provides core behavior but lacks details on timeout handling, error conditions, and output format nuances. Moderate completeness for a line-reading tool.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema coverage is 80%, and the description adds value by explaining 'reads until the newline character' and 'uses the connection's newline setting', complementing schema descriptions for newline and max_bytes.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states 'Read a line from the serial port', specifying the verb and resource. It distinguishes from siblings like serial.read (raw bytes) and serial.read_until (custom terminator) by mentioning newline-based reading.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description implies usage context (reading a line) and mentions the default newline behavior, but lacks explicit guidance on when to use this tool vs alternatives like serial.read or serial.read_until.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Read from the serial port until a delimiter string is received or max_bytes is reached.
| Name | Required | Description | Default |
|---|---|---|---|
| connection_id | Yes | ||
| delimiter | No | Delimiter to read until (default \n). | \n |
| timeout_ms | No | Override read timeout (milliseconds). | |
| max_bytes | No | Maximum bytes to read (default 4096). | |
| as | No | Output format (default text). | text |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description must disclose behavioral traits. It only states the stopping conditions (delimiter or max_bytes) but does not mention blocking behavior, timeout consequences, error handling, or connection state effects. This is insufficient for an agent to anticipate tool behavior.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is a single, front-loaded sentence that efficiently conveys the core functionality with no wasted words. It is well-structured for quick agent parsing.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the tool has 5 parameters and no output schema, the description is too minimal. It does not explain return values, what happens when delimiter is not received, or timeout behavior. The missing completeness could lead to incorrect usage.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 80% (4 of 5 parameters have descriptions). The tool description adds no new meaning beyond the schema; it merely restates the delimiter and max_bytes concepts. The 'as' parameter is not mentioned. With high schema coverage, baseline 3 is appropriate.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description uses a specific verb ('Read') and resource ('serial port') and clearly distinguishes from sibling tools like serial.read (no delimiter) and serial.readline (newline only) by specifying 'until a delimiter string' or 'max_bytes'. This makes the purpose unambiguous.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description implies usage for reading serial data with a custom delimiter, but lacks explicit guidance on when to use this tool over alternatives like serial.read or serial.readline. No exclusions or prerequisites are mentioned.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Set the DTR (Data Terminal Ready) control line. Usage is device-specific — check the protocol spec or ask the user.
| Name | Required | Description | Default |
|---|---|---|---|
| connection_id | Yes | ||
| value | Yes | True = high, False = low. |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, and the description does not disclose behavioral traits such as side effects, permissions, or prerequisites. It only warns about device-specificity.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is a single sentence, efficiently front-loading the action and including a necessary warning.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the tool's simplicity and lack of output schema, the description omits important context such as prerequisites (e.g., connection must be open) and return behavior.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Only one of two parameters ('value') has a schema description, and the tool description does not add semantics for the other parameter ('connection_id') or elaborate further.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the verb 'set' and the resource 'DTR control line', which is distinct from sibling tools like serial.set_rts and serial.pulse_dtr.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description provides vague usage guidance ('Usage is device-specific — check the protocol spec or ask the user'), but does not explicitly contrast with alternatives or state when not to use.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Set the RTS (Request To Send) control line. Usage is device-specific — check the protocol spec or ask the user.
| Name | Required | Description | Default |
|---|---|---|---|
| connection_id | Yes | ||
| value | Yes | True = high, False = low. |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description must cover behavioral traits. It states a write operation ('Set') but does not disclose potential side effects, required permissions, or conditions under which the operation might fail. The device-specific warning is helpful but insufficient.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Two short sentences, front-loaded with purpose ('Set the RTS control line'), and no redundant information. Highly efficient.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a simple tool with two parameters and no output schema, the description is adequate but lacks details about error handling, idempotency, or what happens when the line is already in the requested state. The device-specific warning compensates slightly.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 50% (only the 'value' parameter has a description). The tool description adds no extra meaning about parameters like connection_id or valid values beyond the schema's 'True = high, False = low.'
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the action ('Set the RTS control line') and identifies the resource. It does not differentiate from sibling tools like serial.pulse_rts or serial.set_dtr, but the purpose is still clear.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description advises that usage is device-specific and to check the protocol spec or ask the user, implying caution. However, no explicit guidance on when to use this tool versus alternatives like serial.pulse_rts is provided.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Attach a registered spec to a connection session (in-memory only). The spec will be available via serial.spec.get for the duration of this connection. After attaching, check serial.plugin.list for a matching plugin, then present the user with their options: interact with the device using the spec (send commands, execute flows), use plugin shortcut tools if a plugin is loaded, extend an existing plugin with new tools, or create a new plugin using serial.plugin.template.
| Name | Required | Description | Default |
|---|---|---|---|
| connection_id | Yes | ||
| spec_id | Yes | The spec_id from serial.spec.register. |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the burden. It discloses in-memory only behavior and availability via serial.spec.get. However, it omits side effects, error conditions, and what happens on connection closure.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is a single sentence that packs substantial information, but it could benefit from being broken into shorter sentences for improved readability. Overall, it is fairly concise.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the absence of output schema and the presence of many sibling tools, the description is somewhat complete. However, it lacks details on error handling, parameter validation, and the lifecycle of the attached spec relative to the connection.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 50%, and the description does not add meaning to the parameters. 'connection_id' lacks any description, and 'spec_id' is only vaguely referenced. The description fails to compensate for the low schema coverage.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the action (attach), the resource (spec to connection session), and a key characteristic (in-memory only). It effectively distinguishes from sibling tools like serial.spec.register and serial.spec.get.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description provides post-attach steps (check for plugin, present user options) but does not explicitly state when to use this tool versus alternatives like serial.spec.get or serial.plugin.load. Usage context is implied but not fully clarified.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Get the attached spec for a connection (returns null if none attached).
| Name | Required | Description | Default |
|---|---|---|---|
| connection_id | Yes |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations provided, the description carries the full burden. It discloses that the tool returns null if no spec is attached, which is a useful behavioral detail. However, it does not mention error conditions (e.g., invalid connection_id) or side effects.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is a single sentence of 9 words, front-loading the action and resource. Every word is necessary; no filler or redundancy.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a simple getter with one parameter and no output schema, the description is mostly complete. It states the primary function and the special null return. However, it could be improved by noting that the connection must be open or that the spec is retrieved from the current session.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
The schema has 0% description coverage for parameters. The description does not explain the meaning or valid values of connection_id beyond its role in identifying a connection. No examples or references to how to obtain a connection_id are given.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the verb 'Get' and the resource 'attached spec for a connection', including the special return behavior (null if none attached). This distinguishes it from sibling tools like serial.spec.list and serial.spec.read.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
No guidance on when to use this tool vs alternatives. The description implies it is for retrieving the spec currently attached to a given connection, but does not mention alternatives or prerequisites like needing an open connection.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
List all registered specs with their metadata and matching hints.
| Name | Required | Description | Default |
|---|---|---|---|
No parameters | |||
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description must disclose behaviors. It only states the output (metadata and matching hints) but does not mention performance, authentication requirements, or any side effects. The read-only nature is implied but not explicit.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is a single sentence that is concise and front-loaded. Every word is informative and there is no unnecessary content.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a simple list tool with no parameters and no output schema, the description provides adequate context by specifying the scope (all registered specs) and the contents (metadata and matching hints). It is sufficiently complete for an agent to understand the tool's purpose and output.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
There are no parameters, and the schema coverage is 100% (empty schema). The description does not need to add parameter semantics, and the baseline for 0 parameters is 4.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states it lists all registered specs, including metadata and matching hints, and distinguishes itself from sibling tools like serial.spec.get (retrieves a specific spec) and serial.spec.search (searches specs).
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
No guidance is provided on when to use this tool versus alternatives such as serial.spec.search or serial.spec.get. The description does not mention when not to use it or any prerequisites.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Read full spec content, file path, and metadata by spec_id.
| Name | Required | Description | Default |
|---|---|---|---|
| spec_id | Yes |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full burden. It implies a read operation but does not explicitly state it is read-only, nor does it disclose any behavioral traits such as idempotency, side effects, or required permissions.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is a single sentence that conveys the essential information without any waste. It is front-loaded with the action and key outputs.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the simplicity of the tool (one required parameter, no output schema), the description adequately covers what it does and what it returns. It could mention the requirement of spec_id more explicitly, but overall it is sufficient.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 0%, and the description adds minimal value beyond mentioning 'by spec_id'. It does not explain what spec_id is, how to obtain it, or its format, leaving the agent to guess.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the tool reads full spec content, file path, and metadata by spec_id. It uses a specific verb ('Read') and resource ('spec'), making the purpose clear. However, it does not distinguish itself from the sibling tool 'serial.spec.get', which may have overlapping functionality.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
No guidance is provided on when to use this tool versus alternatives like 'serial.spec.get' or 'serial.spec.list'. The description does not mention prerequisites, context, or when not to use it.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Register a spec file in the index. Validates YAML front-matter (requires kind: serial-protocol and name). The file path can be absolute or relative to CWD.
| Name | Required | Description | Default |
|---|---|---|---|
| path | Yes | Path to the spec markdown file. |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries full burden. It discloses validation of YAML front-matter and path handling, but omits important behaviors such as idempotency, permissions required, what happens on validation failure, or whether it overwrites existing registrations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is two sentences, front-loading the core action 'Register a spec file in the index'. Every sentence adds necessary detail without redundancy. Highly efficient.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the simplicity (1 param, no output schema), the description covers validation and path constraints. However, it lacks information about return values or success/failure indicators, which is important for a registration action. The absence of output schema increases the need for descriptive completeness.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema coverage is 100% with a basic description. The description adds meaning beyond schema by clarifying that the path can be absolute or relative to CWD and specifying the YAML front-matter validation requirements, which is valuable context for the agent.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states 'Register a spec file in the index', specifying the action and resource. It also provides distinct validation requirements ('kind: serial-protocol and name'), setting it apart from sibling tools like serial.spec.attach or serial.spec.read.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description implies when to use (to add a spec file to the index) but does not explicitly mention exclusions or alternatives, such as when not to use or when to prefer serial.spec.attach or serial.spec.template. It provides clear context but lacks guidance on selection.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Full-text search over a spec's content. Returns matching snippets with line numbers and surrounding context.
| Name | Required | Description | Default |
|---|---|---|---|
| spec_id | Yes | ||
| query | Yes | Search terms (space-separated). | |
| k | No | Max results to return (default 10). |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries full burden. It discloses the output format (snippets with line numbers and context) but does not mention read-only nature, potential performance impacts on large specs, or error handling (e.g., invalid spec_id).
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Two sentences with no redundant words. The first sentence front-loads the action and resource; the second adds output details. Every part earns its place.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given no output schema, the description adequately describes return values. It could mention error cases or performance implications, but for a straightforward search tool, it is reasonably complete.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 67% (query and k have descriptions, spec_id does not). The tool description adds no additional parameter meaning beyond the schema, so it meets the baseline for this coverage range.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the verb 'search' and the resource 'spec's content', specifying that it returns snippets with line numbers and context. This distinguishes it from sibling tools like serial.spec.get or serial.spec.read which retrieve entire specs.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
No guidance is provided on when to use this tool versus alternatives (e.g., serial.spec.get for full spec retrieval). The description lacks explicit when-to-use or when-not-to-use context.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Return a markdown template for a new serial protocol spec. Optionally pre-fill with a device name.
| Name | Required | Description | Default |
|---|---|---|---|
| device_name | No | Device name to pre-fill in the template. |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations provided, and the description does not disclose any behavioral traits (side effects, auth needs, etc.). It only states the output type.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
One sentence, 16 words, front-loaded. No unnecessary information.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
No output schema, but description adequately explains the return type (markdown template). Lacks detail on template contents but sufficient for a simple tool.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema coverage is 100% with a clear description for 'device_name'. The description adds minimal value beyond confirming optional pre-fill.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the tool returns a markdown template for a new serial protocol spec, with optional pre-fill. It distinguishes from siblings like serial.spec.get and serial.spec.list.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
No guidance on when to use this tool vs alternatives like serial.spec.register or serial.spec.get. No contextual clues for usage.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Return tracing config and event count.
| Name | Required | Description | Default |
|---|---|---|---|
No parameters | |||
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description must disclose behavior. It indicates a read operation but does not state idempotency, side effects, or prerequisites (e.g., whether a serial connection is needed). The lack of behavioral detail limits transparency.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is a single sentence with no wasted words. It is front-loaded and efficiently conveys the tool's purpose.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a simple parameterless tool, the description adequately states what it returns. However, it could mention whether the tool is always available or requires a context, and it lacks any output schema or return value details, which would improve completeness.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
No parameters exist, so baseline is 4. The description adds no parameter-specific meaning, but the schema provides no information either. The description implicitly confirms no parameters are needed.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the tool returns tracing config and event count, a specific verb and resource. It distinguishes from sibling tools like serial.trace.tail, which implies live event viewing, and other serial tools that perform different actions.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
No guidance on when to use this tool versus alternatives like serial.trace.tail or serial.connection_status. The description does not mention prerequisites, context, or scenarios where this tool is appropriate.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Return last N trace events (default 50).
| Name | Required | Description | Default |
|---|---|---|---|
| n | No | Number of recent events to return (default 50). |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Without annotations, the description alone must convey behavioral traits. It indicates a read operation, but does not disclose side effects, permissions needed, error conditions, or behavior when tracing is not active. The transparency is minimal.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is a single concise sentence that efficiently conveys the core functionality. It is front-loaded with the verb, though it could benefit from minor additional context without losing conciseness.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the lack of output schema and annotations, the description fails to explain what trace events are, how they are sourced, or any assumptions about the trace being active. For a simple tool, more context is needed for full understanding.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
The single parameter 'n' is fully described in the schema with its default, and the tool description adds no additional meaning. With 100% schema coverage, the baseline of 3 is appropriate.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the action ('Return'), the resource ('trace events'), and the qualifier ('last N'), with a default value. It distinguishes this tool from siblings like serial.trace.status by specifying it returns events, not status.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
No guidance on when to use this tool versus alternatives, nor any mention of prerequisites or when not to use it. The description is purely functional without usage context.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Write data to a serial port. Returns the number of bytes written.
| Name | Required | Description | Default |
|---|---|---|---|
| connection_id | Yes | ||
| data | Yes | Data to write. | |
| encoding | No | Override encoding for this call (defaults to connection encoding). | |
| append_newline | No | Append the connection's newline character after data (default false). | |
| newline | No | Override newline for append_newline (defaults to connection newline). | |
| as | No | How to interpret 'data': text (encode with encoding), hex, or base64. | text |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries full burden. It only states the action and return value, but does not disclose blocking behavior, error conditions, or prerequisites like port being open.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is a single concise sentence that immediately states the action. However, it could be restructured to front-load key information like required state, but remains efficient.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given 6 parameters, no output schema, and no annotations, the description is insufficient. It omits critical context such as the need for an open connection, encoding behavior, and potential side effects.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema coverage is high (83%), so the description does not need to repeat parameter details. However, the description adds no extra meaning beyond the schema, e.g., does not explain that connection_id refers to an open connection or the effect of encoding options.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the verb 'write' and the resource 'serial port', and specifies the return value ('number of bytes written'). This distinguishes it from sibling tools like serial.read, serial.close, etc.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
No guidance is provided on when to use this tool versus alternatives. For example, it does not mention that a connection must be opened first via serial.open or the expected state of the port.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Recent tool additions, removals, and schema changes observed during successful MCP inspections. Dates show when Glama detected each change.
v0.1.0serial.closeserial.connection_statusserial.connections.listserial.flushserial.list_portsserial.openserial.plugin.listserial.plugin.loadserial.plugin.reloadserial.plugin.templateserial.pulse_dtrserial.pulse_rtsserial.readserial.read_untilserial.readlineserial.set_dtrserial.set_rtsserial.spec.attachserial.spec.getserial.spec.listserial.spec.readserial.spec.registerserial.spec.searchserial.spec.templateserial.trace.statusserial.trace.tailserial.writeEach tool has a distinct purpose: serial I/O, connection management, plugin control, spec management, and tracing are all clearly separated. No two tools overlap in functionality.
All tools follow a consistent prefix pattern 'serial.<category>.<action>' with snake_case (e.g., serial.open, serial.plugin.list, serial.spec.register). This makes the hierarchy predictable and easy to navigate.
27 tools cover many sub-domains (basic I/O, plugins, specs, tracing), which is on the higher side but each tool is justified for a comprehensive serial MCP server. Slightly over-scoped but still well-organized.
The tool set covers all necessary serial operations: open/close, read/write (including line and until), flush, port listing, DTR/RTS control, pulse, plus extensibility via plugins and protocol specs, and debugging with tracing. No obvious gaps.
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