Unreal_mcp

A comprehensive Model Context Protocol (MCP) server that enables AI assistants to control Unreal Engine through a native C++ Automation Bridge plugin. Built with TypeScript and C++.

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Table of Contents

• Features
• Getting Started
• Configuration
• Available Tools
• Docker
• Documentation
• Community
• Development
• Contributing

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Features

Architecture

• Native C++ Automation — All operations route through the MCP Automation Bridge plugin
• Dual Transport — Native HTTP/SSE (no bridge needed) or WebSocket via TypeScript bridge
• Dynamic Type Discovery — Runtime introspection for lights, debug shapes, and sequencer tracks
• Graceful Degradation — Server starts even without an active Unreal connection
• On-Demand Connection — Retries automation handshakes with exponential backoff
• Command Safety — Blocks dangerous console commands with pattern-based validation
• Capability Token Auth — Optional token-based authentication for both WS and HTTP transports
• Asset Caching — 10-second TTL for improved performance
• Metrics Rate Limiting — Per-IP rate limiting (60 req/min) on Prometheus endpoint
• Centralized Configuration — Unified class aliases and type definitions

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Getting Started

Prerequisites

• Unreal Engine 5.0–5.8 source-compatibility target. The current complete live acceptance record covers UE 5.7.4 only.

Choose your transport:

• Option A: Native MCP (recommended) — no additional dependencies
• Option B: TypeScript Bridge — requires Node.js 18+

Step 1: Install MCP Server (Option B only — skip for Native MCP)

Skip this step if using Option A: Native MCP Transport (Step 4A below).

NPX (Recommended):

npx unreal-engine-mcp-server

Clone & Build:

git clone https://github.com/ChiR24/Unreal_mcp.git
cd Unreal_mcp
npm install
npm run build
node dist/cli.js

Step 2: Install Unreal Plugin

The MCP Automation Bridge plugin is included at Unreal_mcp/plugins/McpAutomationBridge.

From source (requires a project with code target)

Your project must have a code target (.sln or .xcworkspace). Blueprint-only projects cannot compile native plugins — to convert, add any class via Tools > New C++ Class in the editor.

Method 1: Copy Folder

Copy:  Unreal_mcp/plugins/McpAutomationBridge/
To:    YourUnrealProject/Plugins/McpAutomationBridge/

Method 2: External Plugin Directory (no copy needed)

1. Open Unreal Editor → Edit → Plugins
2. Click Plugin Directories (bottom-left)
3. In Additional Plugin Directories, add the path to Unreal_mcp/plugins/
4. Restart the editor — the plugin will be picked up from the external location

This saves the path in your .uproject file so the plugin stays linked without copying.

The plugin compiles automatically when you open the project — UE detects the .uplugin + Source/ and runs UnrealBuildTool.

Video Guide:

https://github.com/user-attachments/assets/d8b86ebc-4364-48c9-9781-de854bf3ef7d

⚠️ First-Time Project Open: UE may prompt "Would you like to rebuild them now?" — click Yes. If instead you see "Missing Modules — McpAutomationBridge. Engine modules cannot be compiled at runtime. Please build through your IDE." — open your project in Visual Studio (Win) or Xcode (Mac) and build from there. After that, the editor will open normally with the plugin loaded.

Pre-built (works with any project, including Blueprint-only)

Build the plugin once, then distribute the compiled binaries — no IDE or compilation needed on the target machine.

1. Build:

# macOS / Linux
./scripts/package-plugin.sh /path/to/UE_5.6

# Windows
scripts\package-plugin.bat C:\Path\To\UE_5.6

This produces a zip like McpAutomationBridge-v0.5.30-UE5.7-Linux.zip.

2. Install: unzip into YourProject/Plugins/ and open the project. That's it — no compilation step.

Note: pre-built binaries are tied to a specific UE version. A build for 5.6 won't work with 5.5, 5.7, or 5.8.

Step 3: Enable Required Plugins

Enable via Edit → Plugins, then restart the editor.

💡 Optional plugins are auto-enabled by the MCP Automation Bridge plugin when needed. PCG support is compiled for source projects when the project explicitly enables PCG. Versioned release packages for UE 5.2+ include PCG support.

Step 4: Configure MCP Client

Option A: Native MCP Transport (Direct HTTP — no bridge needed)

The plugin includes a built-in MCP Streamable HTTP server. AI clients connect directly to the plugin over HTTP — no TypeScript bridge, no Node.js, no npm. Note: the bAllowNonLoopback setting now applies to both the WebSocket bridge and the native MCP transport. Enabling it binds both surfaces to non-loopback addresses. If you only need LAN access for the WebSocket bridge, do not enable bAllowNonLoopback and instead expose the bridge via a reverse proxy. When bAllowNonLoopback is enabled, always also enable bRequireCapabilityToken — the default-allow loopback posture means any LAN client can otherwise call any tool without authentication.

Enable in Unreal:

1. Edit > Project Settings > Plugins > MCP Automation Bridge
2. Check Enable Native MCP
3. Set port (default: 3000)
4. Optionally set Native MCP Instructions for project-specific guidance
5. Restart the editor

Configure your MCP client to use Streamable HTTP transport at:

http://localhost:3000/mcp

Claude Code:

claude mcp add unreal-engine --transport http http://localhost:3000/mcp

Or manually in ~/.claude/settings.json or project .mcp.json:

{
  "mcpServers": {
    "unreal-engine": {
      "type": "url",
      "url": "http://localhost:3000/mcp"
    }
  }
}

Cursor (.cursor/mcp.json):

{
  "mcpServers": {
    "unreal-engine": {
      "url": "http://localhost:3000/mcp"
    }
  }
}

Verify it works:

• Status bar — look for ● MCP :3000 (2) in the bottom-right of the editor. Green dot = server running, number in parens = active sessions. Click it to open settings.
• Output Log — filter by LogMcpNativeTransport to see connections, tool calls, and session activity:

  LogMcpNativeTransport: Native MCP server started on http://localhost:3000/mcp
  LogMcpNativeTransport: MCP session initialized: ... (client: claude-code 2.1.92, active sessions: 1)
  LogMcpNativeTransport: tools/call: inspect (RequestId=...)
  LogMcpNativeTransport: tools/call completed: ... (tool=inspect, success=true)
  

Features:

• SSE streaming for real-time progress during long operations
• Multiple concurrent sessions (Cursor + Claude Code + others simultaneously)
• Dynamic tool management — core tools load by default, enable more via manage_tools
• Python execution via execute_python action (inline code or .py files)
• Capability token authentication — enable in project settings for network security

Option B: TypeScript Bridge (stdio — classic setup)

Add to your Claude Desktop / Cursor config file:

Using Clone/Build:

{
  "mcpServers": {
    "unreal-engine": {
      "command": "node",
      "args": ["path/to/Unreal_mcp/dist/cli.js"],
      "env": {
        "UE_PROJECT_PATH": "C:/Path/To/YourProject",
        "MCP_AUTOMATION_PORT": "8091"
      }
    }
  }
}

Using NPX:

{
  "mcpServers": {
    "unreal-engine": {
      "command": "npx",
      "args": ["unreal-engine-mcp-server"],
      "env": {
        "UE_PROJECT_PATH": "C:/Path/To/YourProject"
      }
    }
  }
}

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Configuration

Environment Variables

# Required
UE_PROJECT_PATH="C:/Path/To/YourProject"

# Automation Bridge
MCP_AUTOMATION_HOST=127.0.0.1
MCP_AUTOMATION_PORT=8091

# LAN Access (optional)
# SECURITY: Set to true to allow binding to non-loopback addresses (e.g., 0.0.0.0)
# Only enable if you understand the security implications.
MCP_AUTOMATION_ALLOW_NON_LOOPBACK=false

# Logging
LOG_LEVEL=info  # debug | info | warn | error

# Optional
MCP_CONNECTION_TIMEOUT_MS=5000
MCP_REQUEST_TIMEOUT_MS=120000
ASSET_LIST_TTL_MS=10000

# Optional Prometheus metrics endpoint
# Loopback-only by default. Non-loopback metrics requires both explicit opt-in and a token.
# MCP_METRICS_PORT=9100
# MCP_METRICS_HOST=127.0.0.1
# MCP_METRICS_ALLOW_NON_LOOPBACK=false
# MCP_METRICS_TOKEN=change-me

# Custom content mount points (comma-separated)
# Plugins with CanContainContent register mount points beyond /Game/.
# MCP_ADDITIONAL_PATH_PREFIXES=/ProjectObject/,/ProjectAnimation/

LAN Access Configuration

By default, the automation bridge only binds to loopback addresses (127.0.0.1) for security. To enable access from other machines on your network:

TypeScript (MCP Server):

MCP_AUTOMATION_ALLOW_NON_LOOPBACK=true
MCP_AUTOMATION_HOST=0.0.0.0

Unreal Engine Plugin:

1. Go to Edit → Project Settings → Plugins → MCP Automation Bridge
2. Under Security, enable "Allow Non Loopback"
3. Under Connection, set "Listen Host" to 0.0.0.0
4. Restart the editor

⚠️ Security Warning: Enabling LAN access exposes the automation bridge to your local network. Only use on trusted networks with appropriate firewall rules. Enable capability token authentication (Require Capability Token in project settings) to prevent unauthorized access when using LAN mode.

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Available Tools

23 exposed MCP tools in broad all-tools mode. Related actions live directly on their parent tools so clients load less context without losing capabilities.

Blueprints • Materials • Textures • Static Meshes • Skeletal Meshes • Levels • Sounds • Particles • Niagara Systems • Behavior Trees

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Docker

docker build -t unreal-mcp .
docker run -it --rm -e UE_PROJECT_PATH=/project unreal-mcp

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Documentation

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Development

npm run build       # Build TypeScript
npm run lint        # Run ESLint
npm run test:unit   # Run unit tests
npm run test:all    # Run all tests

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Community

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Contributing

Contributions welcome! Please:

• Include reproduction steps for bugs
• Keep PRs focused and small
• Follow existing code style

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License

MIT — See LICENSE