Unity MCP Server

A Model Context Protocol (MCP) server that gives AI assistants like Claude full control over Unity Hub and Unity Editor. Built by AnkleBreaker Studio.

Features

200+ tools covering the full Unity workflow:

Architecture

Claude / AI Assistant ←→ MCP Server (this repo) ←→ Unity Editor Plugin (HTTP bridge)
                                ↕
                          Unity Hub CLI

This server communicates with:

• Unity Hub via its CLI (supports both modern --headless and legacy -- --headless syntax)

• Unity Editor via the companion unity-mcp-plugin which runs an HTTP API inside the editor

Two-Tier Tool System

To avoid overwhelming MCP clients with 200+ tools, the server uses a two-tier architecture:

• Core tools (~70) are always exposed directly

• Advanced tools (~130+) are accessed via a single unity_advanced_tool proxy with lazy loading

This keeps the tool count manageable for clients like Claude Desktop and Cowork while still providing access to every Unity feature. Use unity_list_advanced_tools to discover all advanced tools by category.

Multi-Instance Support

The server automatically discovers all running Unity Editor instances on startup. If only one instance is found, it auto-connects. If multiple instances are running (e.g., main editor + ParrelSync clones), it prompts you to select which one to work with.

Port Resilience — The server includes a multi-layer protection system for reliable multi-project workflows:

• Port Identity Validation — When restoring a saved connection, the server verifies the instance identity (project name + path) matches the expected target. If Unity restarts and a different project grabs the port, the server detects this and re-discovers the correct instance.

• Compile-Time Resilience — During long Unity compiles (when the editor is unresponsive), the server checks the shared instance registry. If the registry entry is fresh (updated within the last 5 minutes via heartbeat), the connection is preserved instead of dropped.

• Crash Detection — The plugin sends a heartbeat every 30 seconds to the instance registry. If Unity crashes and the heartbeat stops, the server detects the stale registry entry (>5 minutes old) and clears it, allowing proper re-discovery.

• Port Affinity — The plugin remembers its last-used port via EditorPrefs and reclaims it on restart, minimizing port swaps across editor restarts.

Quick Start

1. Install the Unity Plugin

In Unity: Window > Package Manager > + > Add package from git URL:

https://github.com/AnkleBreaker-Studio/unity-mcp-plugin.git

2. Install this MCP Server

git clone https://github.com/AnkleBreaker-Studio/unity-mcp-server.git
cd unity-mcp-server
npm install

3. Add to Claude Desktop

Open Claude Desktop > Settings > Developer > Edit Config, and add:

{
  "mcpServers": {
    "unity": {
      "command": "node",
      "args": ["C:/path/to/unity-mcp-server/src/index.js"],
      "env": {
        "UNITY_HUB_PATH": "C:\\Program Files\\Unity Hub\\Unity Hub.exe",
        "UNITY_BRIDGE_PORT": "7890"
      }
    }
  }
}

Restart Claude Desktop. Done!

4. Try It

• "List my installed Unity editors"

• "Show me the scene hierarchy"

• "Create a red cube at position (0, 2, 0) and add a Rigidbody"

• "Profile my scene and show the top memory consumers"

• "List all Shader Graphs in my project"

• "Build my project for Windows"

• "List and start my MPPM multiplayer scenarios"

• "Capture a screenshot of my scene view"

• "Show me the active agent sessions"

Configuration

The Unity plugin also has its own settings accessible via the Dashboard (Window > MCP Dashboard) for port, auto-start, and per-category feature toggles.

Optional Package Support

Some tools activate automatically when their packages are detected in the Unity project:

Features for uninstalled packages return helpful messages explaining what to install.

Requirements

• Node.js 18+

• Unity Hub (for Hub tools)

• Unity Editor with unity-mcp-plugin installed (for Editor tools)

Troubleshooting

"Connection failed" errors — Make sure Unity Editor is open and the plugin is installed. Check the Unity Console for [MCP Bridge] Server started on port 7890.

"Unity Hub not found" — Update UNITY_HUB_PATH in your config to match your installation.

"Category disabled" errors — A feature category may be toggled off. Open Window > MCP Dashboard in Unity to check category settings.

Port conflicts — Change UNITY_BRIDGE_PORT in your Claude config and update the port in Unity's MCP Dashboard settings.

Why AnkleBreaker Unity MCP?

AnkleBreaker Unity MCP is the most comprehensive MCP integration for Unity, purpose-built to leverage the full power of Claude Cowork and other AI assistants. Here's how it compares to alternatives:

Feature Comparison

Cost Comparison

AnkleBreaker Unity MCP is completely free and open source. The prices below reflect only the cost of the AI assistant (Claude) itself — the MCP plugin and server are $0.

Key Advantages

vs. Bezi: Bezi runs as a proprietary Unity plugin with its own credit-based billing — $20–$200/mo on top of your AI subscription. It has historically suffered from freezing the Unity Editor during AI tasks, blocking your workflow. AnkleBreaker MCP is completely free and open source, runs entirely in the background with zero editor impact, and offers 6x more tools — the only cost is your existing Claude subscription.

vs. Coplay MCP: Coplay MCP provides 34 tools across ~5 categories. AnkleBreaker MCP delivers 200+ tools across 30+ categories including advanced features like physics raycasts, terrain editing, shader graph management, profiling, NavMesh, particle systems, and MPPM multiplayer — none of which exist in Coplay. Our two-tier lazy loading system is specifically optimized for Claude Cowork's tool limits.

vs. Unity AI: Unity AI (successor to Muse) is built into Unity 6.2+ but limited to Unity's own AI models and a credit-based "Unity Points" system. It cannot be used with Claude or any external AI assistant, has no MCP support, and offers a fraction of the automation capabilities. AnkleBreaker MCP works with any MCP-compatible AI while giving you full control over which AI models you use.

Support the Project

If Unity MCP helps your workflow, consider supporting its development! Your support helps fund new features, bug fixes, documentation, and more open-source game dev tools.

Sponsor tiers include priority feature requests — your ideas get bumped up the roadmap! Check out the tiers on GitHub Sponsors or Patreon.

What's New in v2.22.2

• Multi-project port identity — The server now validates that a persisted instance selection actually matches the expected project (by name and path) before reconnecting. If a different Unity project grabbed the same port after a restart, the server detects the mismatch and re-discovers the correct instance automatically.

• Compile-time resilience — When a Unity Editor is unresponsive (e.g., during a long compile), the server checks the shared instance registry before dropping the connection. Fresh registry entries (updated by the plugin's 30-second heartbeat) indicate the editor is still alive, preventing unnecessary disconnects during compiles.

• Crash detection — If Unity crashes and the plugin's OnDisable never fires, the registry entry goes stale (no heartbeat updates). The server detects entries older than 5 minutes as crashed instances and clears them, allowing proper re-discovery. The staleness timeout is configurable via UNITY_REGISTRY_STALENESS_TIMEOUT.

• Enhanced instance discovery — Both registry fallback paths in validateSelectedInstance() now check entry staleness, giving three-scenario coverage: normal shutdown (clean unregister), long compile (fresh entry = keep connection), and crash (stale entry = re-discover).

License

MIT with Attribution Requirement — see LICENSE

Any product built with Unity MCP must display "Made with AnkleBreaker MCP" (or "Powered by AnkleBreaker MCP") with the logo. Personal/educational use is exempt.