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Unity-MCP

A bridge between Unity and AI assistants using the Model Context Protocol (MCP).

Overview

Unity-MCP is an open-source implementation of the Model Context Protocol for Unity game development. It enables AI assistants to interact with Unity game environments through a standardized interface, allowing for AI-assisted game development, automated testing, scene analysis, and runtime debugging.

Architecture

The architecture has been simplified to use AILogger for persistence, removing the need for a separate server component:

AI Assistant <-> Unity-MCP STDIO Client <-> Unity Client <-> AILogger
  • AI Assistant: Communicates with the Unity-MCP STDIO Client using the MCP protocol

  • Unity-MCP STDIO Client: Forwards commands to the Unity Client and stores results in AILogger

  • Unity Client: Executes commands in Unity and returns results

  • AILogger: Stores logs and results for later retrieval

The Unity-MCP STDIO Client communicates directly with the Unity Client, which provides endpoints for both code execution and queries. The query tool transforms queries into code execution by wrapping them in a return statement.

Related MCP server: Advanced Unity MCP

Features

  • Execute C# code in the Unity runtime environment

  • Inspect game objects and their components

  • Analyze scene hierarchies and structures

  • Run tests and receive results

  • Invoke methods on game objects and components

  • Modify game state during runtime

Deployment Options

  • Unity Editor Extension: An Editor extension that persists beyond game execution cycles

  • Docker Container: A containerized version that communicates with Unity over the network

  • NPX Package: A Node.js package that can be installed and run via NPX

Documentation

Getting Started

To get started with Unity-MCP, follow these steps:

  1. Clone the repository:

    git clone https://github.com/TSavo/Unity-MCP.git
    cd Unity-MCP
  2. Install dependencies:

    npm install
  3. Build the project:

    npm run build
  4. Start the MCP STDIO client:

    npm start

    This will start the MCP STDIO client that communicates with Unity and uses AILogger for persistence.

    Note: Make sure AILogger is running on http://localhost:3030 or set the AI_LOGGER_URL environment variable to point to your AILogger instance.

  5. Run tests:

    # Run all tests
    npm test
    
    # Run only unit tests
    npm run test:unit
    
    # Run only e2e tests
    npm run test:e2e
    
    # Run tests with a specific pattern
    npm test -- --testNamePattern="should return the server manifest"
    npm run test:unit -- --testNamePattern="should return the server manifest"
    npm run test:e2e -- --testNamePattern="should discover the test server"

For more detailed instructions, see the Installation Guide.

Connecting to AI Assistants

To connect the Unity-MCP bridge to an AI assistant, you need to create an MCP configuration file:

{
  "mcpServers": {
    "unity-ai-bridge": {
      "url": "http://localhost:8080/sse"
    }
  }
}

Place this file in the appropriate location for your AI assistant. For Claude, this would typically be in the Claude Desktop app's configuration directory.

Available Tools

The Unity-MCP bridge provides the following tools:

  1. execute_code: Execute C# code directly in Unity.

  2. query: Execute a query using dot notation to access objects, properties, and methods.

  3. get_logs: Retrieve logs from AILogger.

  4. get_log_by_name: Retrieve a specific log from AILogger.

Usage Examples

Executing Code in Unity

You can execute C# code in Unity using the execute_code tool. The code will be executed in the Unity runtime environment, and the result will be stored in AILogger for later retrieval.

JSON-RPC Request

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "execute_code",
    "arguments": {
      "code": "Debug.Log(\"Hello from Unity!\"); return GameObject.FindObjectsOfType<GameObject>().Length;",
      "timeout": 5000
    }
  }
}

JSON-RPC Response

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "content": [
      {
        "type": "text",
        "text": "{\"status\":\"success\",\"logName\":\"unity-execute-1712534400000\",\"result\":{\"success\":true,\"result\":42,\"logs\":[\"Hello from Unity!\"],\"executionTime\":123}}"
      }
    ]
  }
}

Querying Unity Objects

You can query Unity objects using the query tool. This allows you to access objects, properties, and methods using dot notation.

JSON-RPC Request

{
  "jsonrpc": "2.0",
  "id": 2,
  "method": "tools/call",
  "params": {
    "name": "query",
    "arguments": {
      "query": "Camera.main.transform.position",
      "timeout": 5000
    }
  }
}

JSON-RPC Response

{
  "jsonrpc": "2.0",
  "id": 2,
  "result": {
    "content": [
      {
        "type": "text",
        "text": "{\"status\":\"success\",\"logName\":\"unity-query-1712534400000\",\"result\":{\"success\":true,\"result\":{\"x\":0,\"y\":1,\"z\":-10},\"executionTime\":45}}"
      }
    ]
  }
}

Retrieving Results from AILogger

You can retrieve the results of previous operations from AILogger using the get_log_by_name tool.

JSON-RPC Request

{
  "jsonrpc": "2.0",
  "id": 3,
  "method": "tools/call",
  "params": {
    "name": "get_log_by_name",
    "arguments": {
      "log_name": "unity-execute-1712534400000",
      "limit": 1
    }
  }
}

JSON-RPC Response

{
  "jsonrpc": "2.0",
  "id": 3,
  "result": {
    "content": [
      {
        "type": "text",
        "text": "{\"status\":\"success\",\"name\":\"unity-execute-1712534400000\",\"entries\":[{\"id\":\"123e4567-e89b-12d3-a456-426614174000\",\"name\":\"unity-execute-1712534400000\",\"data\":{\"result\":{\"success\":true,\"result\":42,\"logs\":[\"Hello from Unity!\"],\"executionTime\":123},\"timestamp\":\"2025-04-08T00:00:00.000Z\"},\"timestamp\":\"2025-04-08T00:00:00.000Z\"}]}"
      }
    ]
  }
}

Example Usage

Once the AI assistant has access to the Unity tool, you can ask it to perform tasks like:

Can you execute the following C# code in Unity?

GameObject.Find("Player").transform.position = new Vector3(0, 1, 0);

License

MIT

Author

T Savo (@TSavo)

Available Tools

3 tools
list_files_in_projectC

Lists all the files inside a Unity project.

ParametersJSON Schema
NameRequiredDescriptionDefault
projectNameYes

TDQS

C2.8/5.0
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 states the action ('Lists') but doesn't describe key traits like whether it's read-only (implied but not explicit), what format the output takes (e.g., list of filenames vs. metadata), pagination, error conditions, or permissions required. For a tool with zero annotation coverage, this is a significant gap in transparency.

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 directly states the tool's function without unnecessary words. It's appropriately sized for a simple listing tool and front-loaded with the core action, making it easy to parse quickly.

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 tool's simplicity (1 parameter, no output schema, no annotations), the description is incomplete. It lacks details on parameter semantics, output format, and behavioral context (e.g., read-only nature, error handling). While concise, it doesn't provide enough information for an agent to use the tool effectively without additional assumptions.

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

Parameters2/5

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

The schema has 0% description coverage, so the parameter 'projectName' is undocumented in the schema. The description adds no information about this parameter—it doesn't explain what 'projectName' refers to (e.g., a Unity project identifier), valid formats, or examples. With low schema coverage, the description fails to compensate, leaving the parameter's meaning unclear.

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 verb ('Lists') and resource ('all the files inside a Unity project'), making the tool's purpose immediately understandable. However, it doesn't explicitly differentiate from sibling tools like 'list_projects' (which lists projects) or 'read_file' (which reads file contents), missing the opportunity to clarify its specific scope within the toolset.

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. It doesn't mention prerequisites (e.g., needing an existing project), exclusions, or comparisons to siblings like 'list_projects' for project-level listing or 'read_file' for accessing file details. This leaves the agent without context for tool selection.

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

list_projectsB

Lists all available Unity projects.

ParametersJSON Schema
NameRequiredDescriptionDefault

No parameters

TDQS

B3.1/5.0
Behavior2/5

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

With no annotations provided, the description carries full burden but only states the basic action. It doesn't disclose behavioral traits like whether results are paginated, sorted, filtered, or include metadata; whether it requires authentication; or what the return format looks like. This leaves significant gaps 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.

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 with zero wasted words. It's appropriately sized for a simple list operation with no parameters.

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?

For a tool with no annotations and no output schema, the description is incomplete. It doesn't explain what 'lists' entails (e.g., format, metadata included) or behavioral aspects, leaving the agent with insufficient context to understand the tool's full behavior beyond its basic purpose.

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

Parameters4/5

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

The input schema has 0 parameters with 100% coverage, so no parameter documentation is needed. The description appropriately doesn't mention parameters, earning a baseline high score since it doesn't need to compensate for schema gaps.

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 action ('Lists') and resource ('all available Unity projects'), making the purpose immediately understandable. It doesn't differentiate from sibling tools like 'list_files_in_project' or 'read_file', which would require mentioning it returns project-level metadata rather than file contents.

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. It doesn't mention that 'list_files_in_project' is for files within a specific project or 'read_file' is for file contents, leaving the agent to infer usage from tool names alone.

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

read_fileC

Reads the contents of a file inside a Unity project.

ParametersJSON Schema
NameRequiredDescriptionDefault
pathYes

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 states the action ('Reads') but doesn't mention potential constraints like file size limits, encoding issues, error handling for missing files, or performance implications. This leaves significant gaps in understanding how the tool behaves beyond its basic function.

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, clear sentence with no wasted words. It front-loads the core action and context efficiently, making it easy to parse and understand at a glance.

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 tool's complexity (reading file contents), lack of annotations, and no output schema, the description is incomplete. It doesn't explain what the tool returns (e.g., text content, binary data, error messages) or address common edge cases like permissions or file existence, making it inadequate for reliable agent use.

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?

The schema description coverage is 0%, so the description must compensate. It implies the 'path' parameter refers to a file path within a Unity project, adding context beyond the schema's minimal type constraints. However, it doesn't specify path format (e.g., relative vs. absolute), supported file types, or examples, leaving some ambiguity.

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 action ('Reads') and target ('contents of a file inside a Unity project'), making the purpose immediately understandable. However, it doesn't explicitly differentiate from sibling tools like 'list_files_in_project' (which enumerates files vs. reading content), leaving room for minor ambiguity.

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 like 'list_files_in_project' or 'list_projects'. It mentions the context ('inside a Unity project') but lacks explicit when-to-use or when-not-to-use instructions, leaving the agent to infer usage scenarios.

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. 3 tool updatesv1.0.0
    • First observedlist_files_in_project
    • First observedlist_projects
    • First observedread_file

TDQS

B3.2/5.0
Disambiguation5/5

Each tool has a clearly distinct purpose: list_projects enumerates projects, list_files_in_project enumerates files within a project, and read_file retrieves file contents. There is no overlap or ambiguity in their functions, making it easy for an agent to select the correct tool.

Naming Consistency5/5

All tool names follow a consistent verb_noun pattern (list_projects, list_files_in_project, read_file) with clear, descriptive verbs. The naming is uniform and predictable, enhancing usability and reducing confusion.

Tool Count3/5

With only 3 tools, the set feels thin for a Unity project management server, as it lacks essential operations like creating, updating, or deleting files or projects. While the tools are well-defined, the count is borderline low for the apparent scope.

Completeness2/5

The tool surface is significantly incomplete for Unity project management. It covers listing and reading but lacks any write, update, or delete operations (e.g., create_project, write_file, delete_file), which are critical for full lifecycle coverage and will likely cause agent failures in many workflows.

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