Unity MCP server

Unity MCP (AI Connector) is a bridge between Large Language Models (LLMs) and Unity, allowing LLMs to understand and utilize Unity's tools based on user requests. It connects to LLM clients like Claude or Cursor through the integrated AI Connector window, enabling AI-assisted development directly within the Unity Editor.

Installation

To install the Unity MCP server:

1. First, install the prerequisites:

   • .NET 9.0
   • OpenUPM-CLI

2. Open a command line in your Unity project folder and run:

   openupm add com.ivanmurzak.unity.mcp
   

Usage

Setting Up the Connection

1. Ensure your project path doesn't contain spaces:

   • ✅ C:/MyProjects/Project
   • ❌ C:/My Projects/Project

2. In Unity, open the AI Connector window by navigating to Window/AI Connector (Unity-MCP).

3. Install an MCP client:

   • Cursor (recommended)
   • Claude Desktop

4. Sign in to your MCP client and click the Configure button.

5. Restart your MCP client and verify that the AI Connector status shows "Connected" or "Connecting...".

Testing the Connection

Test the AI connection by typing a question or task in your client chat, such as:

Explain my scene hierarchy

Available AI Tools

GameObject Operations

• Create, destroy, find, and modify GameObjects
• Change GameObject properties (tag, layer, name, static)
• Set parent relationships
• Duplicate GameObjects

Component Management

• Add components to GameObjects
• Get component information
• Modify component properties and fields
• Set component references
• Destroy components

Editor Control

• Get/Set playmode state
• Get editor windows
• Manage layers and tags
• Execute menu items
• Selection management (get/set)

Asset Management

• Create, find, and refresh assets
• Read and modify asset content
• Rename, delete, and move assets
• Create folders
• Manage materials and shaders

Scene Management

• Create, save, load, and unload scenes
• Get loaded scenes
• Get scene hierarchy

Prefab Operations

• Instantiate prefabs
• Open, modify, save, and close prefabs

Script Management

• Read, update, create, and delete scripts

Creating Custom Tools

To add your own custom tools to the MCP server:

1. Create a class with the McpPluginToolType attribute.
2. Add methods with the McpPluginTool attribute.
3. Optionally add Description attributes to method arguments to help the LLM understand them.
4. Use nullable parameters with default values to mark them as optional.

Here's an example:

[McpPluginToolType]
public class Tool_GameObject
{
    [McpPluginTool
    (
        "MyCustomTask",
        Title = "Create a new GameObject"
    )]
    [Description("Explain here to LLM what is this, when it should be called.")]
    public string CustomTask
    (
        [Description("Explain to LLM what is this.")]
        string inputData
    )
    {
        // do anything in background thread

        return MainThread.Instance.Run(() =>
        {
            // do something in main thread if needed

            return $"[Success] Operation completed.";
        });
    }
}

Note: Use MainThread.Instance.Run(() => when you need to interact with Unity API, which requires running on the main thread. If your tool can run efficiently in a background thread, you can omit this.

How to install this MCP server

For Claude Code

To add this MCP server to Claude Code, run this command in your terminal:

claude mcp add-json "unity-mcp" '{"command":"dotnet","args":["run","--project","path/to/unity-mcp"]}'

See the official Claude Code MCP documentation for more details.

For Cursor

There are two ways to add an MCP server to Cursor. The most common way is to add the server globally in the ~/.cursor/mcp.json file so that it is available in all of your projects.

If you only need the server in a single project, you can add it to the project instead by creating or adding it to the .cursor/mcp.json file.

Adding an MCP server to Cursor globally

To add a global MCP server go to Cursor Settings > Tools & Integrations and click "New MCP Server".

When you click that button the ~/.cursor/mcp.json file will be opened and you can add your server like this:

{
    "mcpServers": {
        "unity-mcp": {
            "command": "dotnet",
            "args": [
                "run",
                "--project",
                "path/to/unity-mcp"
            ]
        }
    }
}

Adding an MCP server to a project

To add an MCP server to a project you can create a new .cursor/mcp.json file or add it to the existing one. This will look exactly the same as the global MCP server example above.

How to use the MCP server

Once the server is installed, you might need to head back to Settings > MCP and click the refresh button.

The Cursor agent will then be able to see the available tools the added MCP server has available and will call them when it needs to.

You can also explicitly ask the agent to use the tool by mentioning the tool name and describing what the function does.

For Claude Desktop

To add this MCP server to Claude Desktop:

1. Find your configuration file:

• macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
• Windows: %APPDATA%\Claude\claude_desktop_config.json
• Linux: ~/.config/Claude/claude_desktop_config.json

2. Add this to your configuration file:

{
    "mcpServers": {
        "unity-mcp": {
            "command": "dotnet",
            "args": [
                "run",
                "--project",
                "path/to/unity-mcp"
            ]
        }
    }
}

3. Restart Claude Desktop for the changes to take effect