Unity MCP Server

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Overview

Unity MCP Server lets LLM-based clients automate the Unity Editor. It focuses on reliable, scriptable workflows with a simple interface and zero or low-configuration setup.

Related MCP server: MCP For Unity

What It Can Do

• Editor automation: Create/modify scenes, GameObjects, components, prefabs, materials

• UI automation: Locate and interact with UI, validate UI state

• Input simulation: Keyboard/mouse/gamepad/touch for playmode testing (Input System only)

• Visual capture: Deterministic screenshots from Game/Scene/Explorer/Window views

• Code base awareness: Safe structured edits and accurate symbol/search powered by bundled C# LSP (no .sln file required)

• Project control: Read/update project/editor settings; read logs, monitor compilation

• Addressables management: Register/organize assets, manage groups, build automation

Performance

Code index tools outperform standard file operations:

Key benefits:

• 128,040 files indexed with 100% coverage

• Non-blocking background index builds (Worker Threads)

• LLM-optimized output with pagination and size limits

For detailed benchmarks, see docs/benchmark-results-2025-12-13.md

Requirements

• Unity 2020.3 LTS or newer

• Node.js 18.x / 20.x / 22.x / 24.x LTS (25+ not supported)

• Claude Desktop or another MCP-compatible client

Installation

Unity Package

Package Manager → Add from git URL:

https://github.com/akiojin/unity-mcp-server.git?path=UnityMCPServer/Packages/unity-mcp-server

Or via OpenUPM:

openupm add com.akiojin.unity-mcp-server

MCP Client Configuration

Configure your MCP client (Claude Desktop example):

• macOS: ~/Library/Application Support/Claude/claude_desktop_config.json

• Windows: %APPDATA%\Claude\claude_desktop_config.json

{
  "mcpServers": {
    "unity-mcp-server": {
      "command": "npx",
      "args": ["@akiojin/unity-mcp-server@latest"]
    }
  }
}

HTTP Mode (for HTTP-only networks)

npx @akiojin/unity-mcp-server --http 6401 --no-telemetry
curl http://localhost:6401/healthz

Quick Start

1. Install the Unity package (Git URL or OpenUPM)

2. Configure your MCP client with the JSON above

3. Open your Unity project (package starts TCP listener on port 6400)

4. Launch your MCP client (it connects to the Node server)

5. Test the connection with ping

Tip: npx @akiojin/unity-mcp-server@latest downloads and runs the latest build without cloning.

Architecture

┌────────────────┐        JSON-RPC (MCP)        ┌──────────────────────┐
│  MCP Client    │ ───────────────────────────▶ │  Node MCP Server     │
│ (Claude/Codex/ │ ◀─────────────────────────── │ (@akiojin/unity-     │
│   Cursor …)    │        tool responses        │ mcp-server)          │
└────────────────┘                              └──────────┬───────────┘
                                                         TCP│6400
                                                            ▼
                                                   ┌───────────────────┐
                                                   │  Unity Editor     │
                                                   │  (Package opens   │
                                                   │   TCP listener)   │
                                                   └───────────────────┘

Configuration

Configuration is optional; defaults work without any config file.

Node-side configuration uses environment variables only, and Unity-side host/port lives in Project Settings.

See docs/configuration.md.

Tools

Unity MCP Server ships 100+ tools. Use the search_tools meta-tool to discover the right tool quickly.

For clients with strict tool-count limits, you can filter exposed tools by category:

export UNITY_MCP_TOOL_INCLUDE_CATEGORIES=system,scene,gameobject,analysis,script
export UNITY_MCP_TOOL_EXCLUDE_CATEGORIES=ui,input,addressables,video,screenshot,profiler

See docs/tools.md for discovery tips and the recommended Code Index workflow.

Note: find_refs supports paging via startAfter and returns cursor when results are truncated.

Claude Code Skills

This package includes Claude Code skills that provide workflow-oriented guidance for effectively using the 108+ tools.

Available Skills

Installation

Install as a Claude Code plugin from GitHub:

# Step 1: Add marketplace
/plugin marketplace add akiojin/unity-mcp-server

# Step 2: Install plugin
/plugin install unity-mcp-server@unity-mcp-server

Or manually copy the .claude/skills/ directory to your project.

Usage

Skills activate automatically when you mention related keywords. You can also invoke them directly:

# Ask about C# editing workflow
"How do I edit Unity C# scripts?"

# Ask about scene management
"Create a new scene with basic lighting"

# Ask about testing
"How do I simulate keyboard input in playmode?"

Troubleshooting

See docs/troubleshooting/README.md.

OpenUPM Scoped Registry

To use OpenUPM packages, add the scoped registry to your project:

Via Project Settings

1. Edit > Project Settings > Package Manager

2. Under Scoped Registries, click +

3. Add:

   • Name: OpenUPM

   • URL: https://package.openupm.com

   • Scopes: com.akiojin, com.akiojin.unity-mcp-server

Via manifest.json

"scopedRegistries": [
  {
    "name": "OpenUPM",
    "url": "https://package.openupm.com",
    "scopes": ["com.akiojin", "com.akiojin.unity-mcp-server"]
  }
]

Repository Structure

.unity/
├── cache/           # Local caches (git-ignored)
└── capture/         # Screenshots/videos (git-ignored)

UnityMCPServer/
├── Packages/unity-mcp-server/  # UPM package (source)
└── Assets/                     # Samples only

mcp-server/          # Node MCP server

csharp-lsp/          # Roslyn-based LSP tool

Feature Documentation

All features are documented with SDD format: specs/

Contributing

See CONTRIBUTING.md for development setup, commit guidelines, and PR process.

Development Documentation

For internal development details (Spec Kit, release process, LLM optimization):

• docs/README.md

• docs/development.md

• CLAUDE.md

License

MIT License - see LICENSE file.