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.

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

• MCP Architecture: Overview of the MCP architecture and namespaces
• MCP STDIO Client: Information about the MCP STDIO client and its logging capabilities
• Query Tool: Detailed information about the query tool and how it works
• AILogger Integration: Detailed information about the AILogger integration
• API Reference: Detailed information about the API endpoints
• Installation Guide: Step-by-step instructions for installing and setting up Unity-MCP
• Development Guide: Information about the development environment and workflow
• Hot Reloading Guide: Detailed information about hot reloading in the development environment
• Hot Reloading Quick Reference: Quick reference guide for hot reloading commands and tips
• Contributing Guide: Guidelines for contributing to the project

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().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)