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mkusaka

MCP Shell Server

by mkusaka
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TypeScript
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MCP Shell Server

A server that uses the Model Context Protocol (MCP) to execute shell commands. It functions as a bridge that allows AI agents to safely execute shell commands.

Features

  • Execute shell commands (single-line and multi-line support)

  • Support for various shells (bash, zsh, fish, powershell, cmd, etc.)

  • Detailed error handling and logging

  • MCP Inspector compatible

Related MCP server: Command Executor MCP Server

Installation

From npm (as a user)

# Using npm
npm install -g @mkusaka/mcp-shell-server

# Using yarn
yarn global add @mkusaka/mcp-shell-server

# Using pnpm
pnpm add -g @mkusaka/mcp-shell-server

From source (for development)

# Clone the repository
git clone https://github.com/mkusaka/mcp-shell-server.git
cd mcp-shell-server

# Install dependencies
pnpm install

# Build the project
pnpm build

MCP Configuration

Cursor Configuration

Add the following to your Cursor configuration file (~/.cursor/config.json):

{
  "mcpServers": {
    "shell": {
      "command": "npx",
      "args": ["-y", "@mkusaka/mcp-shell-server"]
    }
  }
}

Cline Integration

Cline is a VS Code extension that allows you to use MCP servers with Claude AI. To set up this MCP shell server with Cline:

  1. Open your Cline MCP settings file:

    • macOS: ~/Library/Application Support/Code/User/globalStorage/saoudrizwan.claude-dev/settings/cline_mcp_settings.json

    • Windows: %APPDATA%/Code/User/globalStorage/saoudrizwan.claude-dev/settings/cline_mcp_settings.json

    • Linux: ~/.config/Code/User/globalStorage/saoudrizwan.claude-dev/settings/cline_mcp_settings.json

  2. Add the shell server MCP configuration:

    {
  "mcpServers": {
    "shell": {
      "command": "npx",
      "args": ["-y", "@mkusaka/mcp-shell-server"],
      "disabled": false,
      "autoApprove": []
    }
  }
}

    Alternatively, if you want to use a locally installed package:

    {
  "mcpServers": {
    "shell": {
      "command": "node",
      "args": ["/path/to/mcp-shell-server/dist/index.js"],
      "disabled": false,
      "autoApprove": []
    }
  }
}

Rule Configuration

Add the following to your AI assistant's rules or prompt:

You have MCP Shell tools at your disposal. Follow these rules regarding Shell tool usage:
1. ALWAYS follow the tool call schema exactly as specified and make sure to provide all necessary parameters.
2. **NEVER refer to tool names when speaking to me.** For example, instead of saying 'I need to use the shell_exec tool to run this command', just say 'I'll run that command for you'.
3. Only use Shell tools when they are necessary. If my task is general or you already know the answer, just respond without calling tools.
4. When I ask you to execute shell commands, use the appropriate tool to:
   - Run single-line commands
   - Run multi-line commands (using heredoc syntax when appropriate)
   - Execute file operations, git commands, or system utilities
   - Provide system information when relevant
5. Always be careful with shell commands that might modify the system, and explain what the command will do before executing it.
6. If a shell command produces an error, explain what went wrong in simple terms and suggest ways to fix it.

Usage

Direct Execution

node dist/index.js
# or as an executable
./dist/index.js

Development Mode

pnpm dev

Testing with MCP Inspector

pnpm inspect

Command Line Arguments

-s, --shell <shell>  Specify the path to the shell to use
-w, --working-dir <directory>  Specify the working directory for command execution
-h, --help           Display help message
-V, --version        Display version information

Tool Reference

shell_exec

Executes commands in the specified shell.

Parameters:

  • command (string, required): The shell command to execute

  • workingDir (string, optional): The working directory to execute the command in. Must be under $HOME.

Resource Reference

The server provides the following system information as resources:

hostname

Returns the hostname of the system.

URI: hostname://

platform

Returns the operating system platform.

URI: platform://

shell

Returns the shell path being used by the server.

URI: shell://

username

Returns the current username.

URI: username://

system-info

Returns comprehensive system information in JSON format, including:

  • hostname

  • platform

  • shell

  • username

  • CPU count

  • Total memory

  • Free memory

  • System uptime

Usage Examples

Basic Command Execution

{
  "name": "shell_exec",
  "parameters": {
    "command": "echo Hello, World!"
  }
}

Multi-line Command (Heredoc) Execution

{
  "name": "shell_exec",
  "parameters": {
    "command": "cat << EOF | grep 'example'\nThis is an example text.\nAnother line without the keyword.\nEOF"
  }
}

Development

Project Structure

src/
├── index.ts                # Main entry point
└── shell-server/
    ├── index.ts            # Shell server implementation
    └── lib/
        └── logger.ts       # Logging configuration

Logging

Logs are written to the mcp-shell.log file.

License

MIT

Available Tools

1 tool
shell_execC

Executes commands in the specified shell with detailed error handling and output capture

ParametersJSON Schema
NameRequiredDescriptionDefault
commandYesThe shell command to execute in the configured shell environment
workingDirNoOptional working directory to execute the command in (must be under $HOME for security)

TDQS

C2.9/5.0
Behavior2/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations provided, the description carries the full burden of behavioral disclosure. It mentions 'detailed error handling and output capture' which adds some context beyond basic execution, but fails to address critical aspects like security implications, permission requirements, rate limits, or what happens when commands fail. For a shell execution tool with zero annotation coverage, this leaves significant gaps.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single, efficient sentence that front-loads the core purpose ('Executes commands in the specified shell') and adds value with secondary capabilities ('with detailed error handling and output capture'). Every word earns its place with zero waste.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness2/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the complexity of shell execution (security risks, variable outputs) and the absence of both annotations and an output schema, the description is insufficient. It doesn't explain return values, error formats, or security constraints beyond the schema's workingDir note. For a potentially dangerous tool with no structured safety indicators, more descriptive context is needed.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the schema already documents both parameters thoroughly. The description adds no additional parameter semantics beyond what's in the schema (e.g., no examples of command syntax, working directory constraints beyond security). The baseline score of 3 reflects adequate schema coverage without description enhancement.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool's purpose: 'Executes commands in the specified shell' with additional capabilities for 'detailed error handling and output capture'. It uses specific verbs ('executes', 'capture') and identifies the resource ('shell commands'). However, there are no sibling tools mentioned, so differentiation from alternatives cannot be evaluated.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

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, prerequisites, or security considerations. It mentions 'detailed error handling and output capture' which implies some context, but offers no explicit when/when-not instructions or named alternatives.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

Tool Schema Changelog

Recent tool additions, removals, and schema changes observed during successful MCP inspections. Dates show when Glama detected each change.

  1. 1 tool updatev1.0.0
    • First observedshell_exec
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TDQS

B3.1/5.0
Disambiguation5/5

With only one tool, there is no possibility of ambiguity or overlap between tools. The tool's purpose is clearly defined and distinct by default.

Naming Consistency5/5

A single tool inherently has perfect naming consistency, as there are no other tools to compare against. The name 'shell_exec' follows a clear verb_noun pattern.

Tool Count2/5

A single tool is generally too few for a server's purpose, as it limits functionality and may indicate an incomplete surface. However, for a simple shell execution server, it could be minimally viable but lacks breadth.

Completeness2/5

The tool provides basic shell command execution, but there are obvious gaps such as no tools for listing available commands, managing shell sessions, or handling file operations, making the surface severely incomplete for typical shell-related tasks.

Maintenance

ActivityInactive
ResponsivenessNo issues

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