Unity MCP server

Unity MCP (Model Context Protocol) is a bridge between Large Language Models (LLMs) and Unity, allowing AI to understand and utilize Unity's tools through a server-client architecture. It enables LLMs to perform operations in the Unity Editor based on natural language requests, making development workflows more efficient.

Installation

To install the Unity MCP server and plugin:

1. First, install the required 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

Basic Setup

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

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

2. Open your Unity project and navigate to Window/AI Connector (Unity-MCP).

3. Install an MCP client:

   • Cursor (recommended)
   • Claude Desktop

4. Sign in to your MCP client

5. Click Configure in your MCP client

6. Restart your MCP client

7. Verify that the AI Connector status shows "Connected" or "Connecting..."

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

   Explain my scene hierarchy
   

Creating Custom Tools

You can extend Unity-MCP functionality by creating custom tools:

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 indicate optional arguments

Here's an example of a custom tool:

[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.Run(() =>
        {
            // do something in main thread if needed

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

Available AI Tools

Unity MCP currently supports various tool categories:

GameObject Operations

• Create, destroy, find, set parent, and duplicate GameObjects
• Manage components: add, get, modify, and destroy

Editor Functions

• Get and set playmode state
• Get and set selection

Prefab Management

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

Asset Handling

• Create, find, refresh, read, modify, rename, delete, and move assets
• Create folders

Scene Operations

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

Material and Shader Tools

• Create and modify materials
• List all shaders

Script Management

• Read, update, create, and delete scripts

Many more tools are planned for future implementation, including ScriptableObject management, debug features, and package operations.

How to add this MCP server to 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 > MCP and click "Add new global MCP server".

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

{
    "mcpServers": {
        "cursor-rules-mcp": {
            "command": "npx",
            "args": [
                "-y",
                "cursor-rules-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 explictly ask the agent to use the tool by mentioning the tool name and describing what the function does.