funplay-unity-mcp

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Funplay MCP for Unity is an MIT-licensed Unity Editor MCP server that lets AI assistants like Claude Code, Cursor, LM Studio, Windsurf, Codex, and VS Code Copilot operate directly inside your running Unity project.

Describe your game in one sentence — your AI assistant builds it in Unity through Funplay MCP for Unity's 154 built-in tools for scene creation, script generation, runtime validation, input simulation, performance analysis, and editor automation.

"Build a snake game with a 10x10 grid, food spawning, score UI, and game-over screen"

Your AI assistant handles it through Funplay MCP for Unity: creates the scene, generates all scripts, sets up the UI, and configures the game logic — all from a single prompt.

Quick Start

If you just want to get connected fast, do these three things:

• Install the Unity package from the Git URL
• Start Funplay > MCP Server
• Use the built-in one-click client configuration

1. Install via UPM (Git URL)

In Unity, go to Window → Package Manager → + → Add package from git URL:

https://github.com/FunplayAI/funplay-unity-mcp.git

💡 Before you clone or install, a quick ⭐ on GitHub would be greatly appreciated.

Optional: Install via OpenUPM

If you want Unity Package Manager to show registry-backed package version history and allow version selection, install from OpenUPM instead of Git.

Using the OpenUPM CLI:

openupm add com.gamebooom.unity.mcp

Or add the scoped registry manually in Packages/manifest.json:

{
  "scopedRegistries": [
    {
      "name": "OpenUPM",
      "url": "https://package.openupm.com",
      "scopes": [
        "com.gamebooom"
      ]
    }
  ],
  "dependencies": {
    "com.gamebooom.unity.mcp": "0.5.3"
  }
}

If you installed from a Git URL before, remove the Git dependency first, then install from OpenUPM. Git-installed packages only show the resolved Git version in Unity and do not get the registry-backed Version History list.

2. Start the MCP Server

Menu: Funplay → MCP Server to start the server.

The server starts on http://127.0.0.1:8765/ by default.

Direct in-process HTTP is the default transport. If you need stronger connection continuity across Unity script recompiles or Play Mode domain reloads, enable Experimental Broker Mode in the MCP Server window. It runs a tiny local broker with Unity's bundled Mono, keeps the same 127.0.0.1 port for MCP clients, and requires no client config change.

Open Funplay → Tool Exposure if you want to edit the exact tools exposed by core or full.

Open Funplay → MCP Settings if you need to adjust execute_code safety defaults or plugin debug logging.

3. Configure Your AI Client

Use the built-in One-Click MCP Configuration in the Funplay > MCP Server window first.

Select your target client, click Configure, and the package writes the recommended MCP config entry for you.

For Claude Code, Cursor, and Codex, click Configure + Skills to also install the default project MCP workflow skill.

If you want project-specific AI guidance for the current Unity project, open Funplay → Project Skills to choose supported platforms and install the default unity-mcp-workflow skill.

If you prefer to edit config files manually, use the examples below as fallback references:

{
  "mcpServers": {
    "funplay": {
      "type": "http",
      "url": "http://127.0.0.1:8765/"
    }
  }
}

{
  "mcpServers": {
    "funplay": {
      "url": "http://127.0.0.1:8765/"
    }
  }
}

LM Studio's mcp.json location can vary by version and platform. Prefer Program > Install > Edit mcp.json in LM Studio. Funplay's one-click Configure button opens LM Studio's lmstudio://add_mcp link and only updates an existing config file if one is already present, instead of creating a guessed path.

{
  "mcpServers": {
    "funplay": {
      "url": "http://127.0.0.1:8765/"
    }
  }
}

{
  "servers": {
    "funplay": {
      "type": "http",
      "url": "http://127.0.0.1:8765/"
    }
  }
}

{
  "mcpServers": {
    "funplay": {
      "url": "http://127.0.0.1:8765/"
    }
  }
}

{
  "mcpServers": {
    "funplay": {
      "type": "http",
      "url": "http://127.0.0.1:8765/"
    }
  }
}

[mcp_servers.funplay]
url = "http://127.0.0.1:8765/"

Use the same JSON structure as Cursor unless your local Windsurf version requires a different MCP config format.

4. Verify the Connection

Open your AI client and try a few safe requests first:

• "Call get_scene_info and tell me what scene is open."
• "Read unity://project/context and summarize the current editor state."
• "Use execute_code to return the active scene name."

If those work, the MCP server, resources, and primary execution tool are connected correctly.

5. Start Building

Open your AI client and try: "Create a 3D platformer level with 5 floating platforms"

Before You Start

• This package is Editor-only. It does not add runtime components to your built game.
• The MCP server starts on http://127.0.0.1:8765/ by default.
• Local MCP server settings are stored in UserSettings/FunplayMcpSettings.json.
• The package defaults to the core MCP tool profile to reduce tool-list noise for AI clients. core currently exposes 32 high-signal tools centered on execute_code, play mode control, input simulation, screenshots, performance inspection, logs, compilation checks, structured object location and component editing, editor selection / prefab-stage state, and execute_menu_item as a low-friction fallback. Switch to full in the MCP Server window if you want all 154 tools exposed.
• execute_code safety checks and the stricter filesystem guard are enabled by default from Funplay > MCP Settings. The guard blocks obvious destructive snippets, broad System.IO writes, raw file streams, and absolute/user/system/traversal paths, but it is not a complete sandbox. Clients may still override the default per call with the optional safety_checks argument.
• Plugin debug logging is off by default and can also be enabled from Funplay > MCP Settings. Warnings and errors are always written to the Unity Console.
• All exposed MCP tools run directly. There is no extra approval toggle.
• Menu: Funplay > Check for Updates can refresh Git installs in place or download and import the latest unitypackage automatically.

Why This Project

• execute_code First — Optimized around one in-memory C# execution tool for rich editor/runtime orchestration. See execute_code: In-Memory C# Execution below for details.
• Default Safety Checks — execute_code now has persistent default-on safety toggles, including a stricter filesystem guard for clients that do not expose per-call arguments clearly
• Play Mode Automation — Enter play mode, simulate keyboard/mouse input, capture screenshots, inspect logs, and validate behavior from the same MCP session
• Project Context Built In — Exposes live resources for project state, active scene, selection, compilation, console output, and MCP interaction history
• Focused by Default, Full When Needed — core exposes a compact high-signal toolset; full exposes all 154 tools
• Single Unity Package — No extra approval UI, no external daemon to click through, and no Python requirement for the Unity-side plugin itself
• Extensible — Add custom tools with attribute-based discovery, or connect Unity to external MCP services when needed

Highlights

• 154 Built-in Tools — Scene editing, assets, scripts, play mode control, screenshots, performance analysis, prompts, resources, structured object location, SerializedObject-based component editing, editor-state inspection, menu-item fallback, and editor automation across 35 modules
• Structured Returns + instanceId Chaining — Tools return {success, message, data} JSON with stable instanceId fields so agents can chain by_id calls reliably instead of re-resolving by name
• IFunplayCommand for execute_code — New snippet template with auto-Undo (ctx.RegisterObjectCreation/Modification/DestroyObject), st