Unity MCP - AI Assistant Integration for Unity Editor

Model Context Protocol (MCP) server that enables AI assistants like Claude, Codex, and Cursor to automate Unity Editor tasks and game development workflows.

Features

Zero telemetry - Completely private Unity automation. No data collection.
40+ built-in tools - Create GameObjects, run tests, build projects, manipulate scenes through AI.
Simple extension API - Add custom AI tools with a single attribute.

Requirements

Unity 6 or later
Any MCP client: Claude Code, Claude Desktop, Codex, Cursor, or other AI assistants

Installation

Open Unity Package Manager (Window → Package Manager)
Click + → "Add package from git URL"
Enter the URL of whichever version you want

Latest Version (Recommended)

To install the latest version:

https://github.com/Bluepuff71/UnityMCP.git?path=/Package

Specific Version (If I messed something up)

To install a specific version, append #version tag:

https://github.com/Bluepuff71/UnityMCP.git?path=/Package#2026.01.26

See Releases for available versions.

Setup

Claude Code

claude mcp add unity-mcp --transport http http://localhost:8080/

Claude Desktop

Add this to your Claude Desktop configuration file:

macOS: ~/Library/Application Support/Claude/claude_desktop_config.json

Windows: %APPDATA%\Claude\claude_desktop_config.json

{
  "mcpServers": {
    "unity-mcp": {
      "command": "npx",
      "args": ["-y", "mcp-remote", "http://localhost:8080/"]
    }
  }
}

Restart Claude Desktop after saving.

Other MCP Clients (Codex, Cursor, etc.)

Unity MCP runs an HTTP server at http://localhost:8080/. Any MCP client with HTTP transport support can connect directly. For stdio-only clients, use the mcp-remote bridge as shown above.

Note: Configurations for clients other than Claude Code have not been tested. Open a PR!

How Unity Editor Automation Works

Unity MCP uses a native C plugin to maintain an HTTP server on a background thread, independent of Unity's C# scripting domain. This architecture ensures the AI assistant connection remains active during script recompilation.

┌─────────────────┐
│  MCP Client     │
│  (Claude, etc.) │
└────────┬────────┘
         │ HTTP
         ▼
┌─────────────────────────────────────┐
│  Native Plugin (C)                  │
│  - HTTP server on background thread │
│  - Survives domain reloads          │
└────────┬────────────────────────────┘
         │
         ▼
┌─────────────────────────────────────┐
│  Unity C# (main thread)             │
│  - Executes tools when available    │
│  - Returns "recompiling" during     │
│    domain reload                    │
└─────────────────────────────────────┘

When Unity recompiles scripts, the C# domain unloads temporarily. During this time, the native plugin continues accepting HTTP requests but returns a "Unity is recompiling" error instead of disconnecting. Once recompilation completes, requests are forwarded to Unity's main thread for execution.

Adding Custom AI Tools

Create a static method and mark it with [MCPTool]:

using UnityMCP.Editor;
using UnityEngine;

public static class MyCustomTools
{
    [MCPTool("hello_world", "Says hello to the specified name")]
    public static string SayHello(
        [MCPParam("name", "Name to greet", required: true)] string name)
    {
        return $"Hello, {name}!";
    }

    [MCPTool("create_cube_at", "Creates a cube at specified position")]
    public static object CreateCube(
        [MCPParam("x", "X coordinate", required: true)] float x,
        [MCPParam("y", "Y coordinate", required: true)] float y,
        [MCPParam("z", "Z coordinate", required: true)] float z)
    {
        GameObject cube = GameObject.CreatePrimitive(PrimitiveType.Cube);
        cube.transform.position = new Vector3(x, y, z);
        cube.name = "Custom Cube";

        return new
        {
            success = true,
            message = $"Created cube at ({x}, {y}, {z})",
            instanceID = cube.GetInstanceID()
        };
    }
}

Tools are automatically discovered on domain reload. No registration needed.

Adding Custom Resources

Resources expose read-only data to AI assistants. Use [MCPResource]:

using UnityMCP.Editor;
using UnityEngine;

public static class MyCustomResources
{
    [MCPResource("unity://player/stats", "Current player statistics")]
    public static object GetPlayerStats()
    {
        var player = GameObject.Find("Player");
        if (player == null)
            return new { error = "Player not found" };

        return new
        {
            position = player.transform.position,
            health = player.GetComponent<Health>()?.CurrentHealth ?? 0,
            isGrounded = player.GetComponent<CharacterController>()?.isGrounded ?? false
        };
    }
}

Resources use URI patterns (e.g., unity://player/stats) and are read via resources/read.

License

GPLv3 - see LICENSE file for details.

Unity MCP