Unity MCP (Server + Plugin)

Unity Version	Editmode	Playmode	Standalone
2022.3.61f1
2023.2.20f1
6000.0.46f1

AI gate to Unity Editor and Unity player's build.

Supports custom tool if any exists in your source code of a Unity project.

AI Tools

Installation

1. Install .NET 9.0
2. Install OpenUPM-CLI

• Open command line in Unity project folder
• Run the command

openupm add com.ivanmurzak.unity.mcp

Usage

1. Go 👉 Tools/Unity-MCP/Server/Print Config. It prints into Console window in Unity Editor the json string.
2. Copy the json string.
3. Insert the json string into your MCP Client app:

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

Add custom tool

⚠️ Not yet supported. There is a blocker issue in csharp-sdk for MCP server. Waiting for solution.

Unity-MCP is designed to support custom tool development by project owner. MCP server takes data from Unity plugin and exposes it to a Client. So anyone in the MCP communication chain would receive the information about a new tool. Which LLM may decide to call at some point.

To add a custom tool you need:

1. To have a class with attribute McpPluginToolType.
2. To have a method in the class with attribute McpPluginTool.
3. [optional] Add Description attribute to each method argument to let LLM to understand it.
4. [optional] Use string? optional = null properties with ? and default value to mark them as optional for LLM.

Take a look that the line => MainThread.Run(() => it allows to run the code in Main thread which is needed to interact with Unity API. If you don't need it and running the tool in background thread is fine for the tool, don't use Main thread for efficience purpose.

[McpPluginToolType]
public class Tool_GameObject
{
    [McpPluginTool
    (
        "GameObject_Create",
        Title = "Create a new GameObject",
        Description = "Create a new GameObject."
    )]
    public string Create
    (
        [Description("Path to the GameObject (excluding the name of the GameObject).")]
        string path,
        [Description("Name of the GameObject.")]
        string name
    )
    => MainThread.Run(() =>
    {
        var targetParent = string.IsNullOrEmpty(path) ? null : GameObject.Find(path);
        if (targetParent == null && !string.IsNullOrEmpty(path))
            return $"[Error] Parent GameObject '{path}' not found.";

        var go = new GameObject(name);
        go.transform.position = new Vector3(0, 0, 0);
        go.transform.rotation = Quaternion.identity;
        go.transform.localScale = new Vector3(1, 1, 1);
        if (targetParent != null)
            go.transform.SetParent(targetParent.transform, false);

        EditorUtility.SetDirty(go);
        EditorApplication.RepaintHierarchyWindow();

        return $"[Success] Created GameObject '{name}' at path '{path}'.";
    });
}

Contribution

Feel free to add new tool into the project.

1. Fork the project.
2. Implement new tool in your forked repository.
3. Create Pull Request into original Unity-MCP repository.