MCP Unreal

mcp-unreal

MCP (Model Context Protocol) server that gives AI coding agents complete autonomous control over an Unreal Engine 5.7 project. Single Go binary, zero external dependencies.

Build, test, manipulate the editor, edit Blueprints, generate procedural meshes, and look up UE API documentation — all through 49 MCP tools that any MCP-compatible agent can call directly.

Quick Start

# Install
go install github.com/remiphilippe/mcp-unreal/cmd/mcp-unreal@latest

# Build the documentation index
mcp-unreal --build-index

# Register with your AI coding tool (see Setup section below)

Prerequisites

• Go 1.25+ — install
• Unreal Engine 5.7 — for build/test tools and editor interaction
• Remote Control API plugin — enabled in UE (see Enabling Remote Control API below)
• MCPUnreal editor plugin — for advanced editor tools (see plugin/README.md)

Installation

From Source

git clone https://github.com/remiphilippe/mcp-unreal.git
cd mcp-unreal
make build

Pre-built Binaries

Download from GitHub Releases — available for macOS, Linux, and Windows on both amd64 and arm64.

Enabling Remote Control API

The Remote Control API is a built-in UE plugin that provides HTTP access to actor properties and function calls on port 30010. mcp-unreal uses it for get_property, set_property, call_function, and move_actor tools.

1. Open your project in Unreal Editor
2. Go to Edit > Plugins
3. Search for "Remote Control API"
4. Check the Enabled checkbox
5. Restart the editor when prompted

To verify it's running:

curl http://localhost:30010/remote/info

You should get a JSON response with the API version. If the connection is refused, the plugin is not enabled or the editor isn't running.

Install the UE Plugin

Copy the plugin/ directory into your project's Plugins/ folder:

cp -r plugin/ /path/to/YourProject/Plugins/MCPUnreal/

Rebuild the project. The plugin starts an HTTP server on port 8090 when the editor loads. See plugin/README.md for details.

Setup by Client

mcp-unreal works with any MCP-compatible AI coding tool. Below are setup instructions for each.

Note: Replace /path/to/mcp-unreal with the actual path to your built binary (e.g. the output of go install or make build). Set MCP_UNREAL_PROJECT to your .uproject file path or project root directory.

Claude Code

CLI registration:

claude mcp add mcp-unreal -- /path/to/mcp-unreal

Config file (.mcp.json at project root, or ~/.claude.json for global):

{
  "mcpServers": {
    "mcp-unreal": {
      "type": "stdio",
      "command": "/path/to/mcp-unreal",
      "env": {
        "MCP_UNREAL_PROJECT": "/path/to/MyProject/MyProject.uproject"
      }
    }
  }
}

Cursor

Config file (.cursor/mcp.json at project root, or ~/.cursor/mcp.json for global):

{
  "mcpServers": {
    "mcp-unreal": {
      "command": "/path/to/mcp-unreal",
      "env": {
        "MCP_UNREAL_PROJECT": "/path/to/MyProject/MyProject.uproject"
      }
    }
  }
}

After saving, enable via Cursor Settings > MCP Servers.

OpenAI Codex CLI

CLI registration:

codex mcp add mcp-unreal -- /path/to/mcp-unreal

Config file (.codex/config.toml at project root, or ~/.codex/config.toml for global):

[mcp_servers.mcp-unreal]
command = "/path/to/mcp-unreal"
args = []
tool_timeout_sec = 120

[mcp_servers.mcp-unreal.env]
MCP_UNREAL_PROJECT = "/path/to/MyProject/MyProject.uproject"

Increase tool_timeout_sec for build_project and run_tests which can take 60+ seconds.

VS Code with GitHub Copilot

Requires VS Code 1.99+ with GitHub Copilot Agent Mode enabled.

Config file (.vscode/mcp.json at project root):

{
  "servers": {
    "mcp-unreal": {
      "type": "stdio",
      "command": "/path/to/mcp-unreal",
      "env": {
        "MCP_UNREAL_PROJECT": "${workspaceFolder}"
      }
    }
  }
}

Windsurf

Config file (~/.codeium/windsurf/mcp_config.json):

{
  "mcpServers": {
    "mcp-unreal": {
      "command": "/path/to/mcp-unreal",
      "env": {
        "MCP_UNREAL_PROJECT": "/path/to/MyProject/MyProject.uproject"
      }
    }
  }
}

Cline (VS Code Extension)

Open the Cline panel > MCP Servers icon > Configure tab > Advanced MCP Settings, then add:

{
  "mcpServers": {
    "mcp-unreal": {
      "command": "/path/to/mcp-unreal",
      "env": {
        "MCP_UNREAL_PROJECT": "/path/to/MyProject/MyProject.uproject"
      }
    }
  }
}

Zed

Config file (~/.config/zed/settings.json):

{
  "context_servers": {
    "mcp-unreal": {
      "command": "/path/to/mcp-unreal",
      "env": {
        "MCP_UNREAL_PROJECT": "/path/to/MyProject/MyProject.uproject"
      }
    }
  }
}

Quick Reference

Recommended System Prompt

For best results, add the following to your project's system prompt (e.g. CLAUDE.md, .cursorrules, .codex/instructions.md, or equivalent). This tells the AI agent how to use the MCP tools effectively.

## Unreal Engine MCP Tools

This project uses mcp-unreal for AI-driven Unreal Engine development. The following MCP tools are available:

### Workflow Guidelines

1. **Always check status first**: Call `status` to verify the editor and plugin connections before attempting editor operations.
2. **Look up docs before writing UE code**: Use `lookup_class` to get class references (inheritance, properties, functions) and `lookup_docs` for API patterns before writing C++ or Blueprint logic.
3. **Build-test cycle**: After editing C++ files, call `build_project` to compile, then `run_tests` to verify. Read build errors carefully — use `lookup_docs` to understand UE APIs.
4. **Actor workflow**: Use `get_level_actors` to discover existing actors, `spawn_actor` to create new ones, `move_actor` to position them, and `set_property`/`get_property` to read/write properties.
5. **Blueprint workflow**: Use `blueprint_query` with operation `list` to find Blueprints, then `list_variables`/`list_functions`/`list_nodes` to inspect them. Use `blueprint_modify` to make changes, and always `compile` after modifications.
6. **Material workflow**: Use `material_ops` with `create` to make new materials, `get_parameters` to inspect existing ones, and `set_parameter` or `set_texture` to modify them.
7. **Save your work**: The editor does not auto-save. After making changes, use `level_ops` with `save_level` or remind the user to save.
8. **PIE testing**: Use `pie_control` with operation `start` to begin a Play In Editor session, `status` to verify it started, and `stop` to end it. Use `capture_viewport` with `include_ui=true` during PIE to see the game view with HUD/menus. Use `player_control` to move the player pawn (`teleport`, `set_rotation`) or reposition the editor viewport camera (`get_camera`, `set_camera`).

### Tool Modes

- **Headless tools** (`build_project`, `run_tests`, `cook_project`, etc.) do NOT require the editor to be running. They invoke UnrealEditor-Cmd directly.
- **Editor tools** (actors, blueprints, materials, etc.) require the Unreal Editor to be open with the MCPUnreal plugin loaded.
- **Documentation tools** (`lookup_docs`, `lookup_class`) are always available — use them liberally.

### Object Paths

Many tools require UE object paths. The format is:
- Actor paths: `/Game/Maps/MapName.MapName:PersistentLevel.ActorName`
- Asset paths: `/Game/Folder/AssetName`
- Engine assets: `/Engine/BasicShapes/Cube`

Use `get_level_actors` to discover actor paths, and `search_assets` to find asset paths.

Tip: For Claude Code, save this as CLAUDE.md in your project root. For Cursor, save as .cursorrules. For Codex, save as .codex/instructions.md.

Configuration

Platform defaults for UE_EDITOR_PATH:

• macOS: /Users/Shared/Epic Games/UE_5.7/Engine/Binaries/Mac/UnrealEditor-Cmd
• Windows: C:\Program Files\Epic Games\UE_5.7\Engine\Binaries\Win64\UnrealEditor-Cmd.exe
• Linux: /opt/UnrealEngine/Engine/Binaries/Linux/UnrealEditor-Cmd

Architecture

                                                    ┌───────────────────────┐
                                                    │   UE 5.7 Editor       │
                                                    │                       │
                                                    │  ┌─────────────────┐  │
                                                    │  │ Remote Control  │  │
                                              ┌────►│  │ API (port 30010)│  │
                                              │     │  │ (built-in)      │  │
                                              │     │  └─────────────────┘  │
┌──────────────┐    stdio     ┌──────────────┐│     │                       │
│  AI Coding   │   JSON-RPC   │              ││     │  ┌─────────────────┐  │
│    Agent     │◄────────────►│  mcp-unreal  │├────►│  │ MCPUnreal       │  │
│ (Claude Code │              │ (Go binary)  ││     │  │ Plugin (port    │  │
│  Cursor, etc)│              │              ││     │  │ 8090)           │  │
└──────────────┘              │ 49 tools     │┘     │  │ • Actors        │  │
                              │ doc index    │      │  │ • Blueprints    │  │
                              │              │      │  │ • Materials     │  │
                              │ ┌──────────┐ │      │  │ • PCG / GAS    │  │
                              │ │ Headless │ │      │  │ • Niagara       │  │
                              │ │ exec.Cmd │─┼──────│──│ • Mesh ops      │  │
                              │ └──────────┘ │      │  │ • Levels        │  │
                              │              │      │  └─────────────────┘  │
                              │ ┌──────────┐ │      │                       │
                              │ │ Bleve    │ │      └───────────────────────┘
                              │ │ Doc Index│ │
                              │ └──────────┘ │      ┌───────────────────────┐
                              │              │──────│ docs/                 │
                              └──────────────┘      │ ├── ue5.7/            │
                                                    │ ├── realtimemesh/     │
                                                    │ └── index.bleve       │
                                                    └───────────────────────┘

Three communication paths:

1. Headless — exec.Command invokes UnrealEditor-Cmd for builds, tests, and cooking. No editor needed.
2. Remote Control API — HTTP PUT to localhost:30010 for property access and function calls. Built into UE.
3. MCPUnreal Plugin — HTTP POST to localhost:8090 for Blueprint editing, asset queries, mesh ops, and other deep editor internals.

See IMPLEMENTATION.md for the full architecture document.

Available Tools (48)

Build & Compile (Headless)

Project & Config (Headless)

Test Automation (Headless)

Actors & Properties (Editor)

Blueprint Editing (Editor)

Animation Blueprint Editing (Editor)

Assets (Editor)

Materials (Editor)

Characters & Input (Editor)

Procedural Content Generation (Editor)

Gameplay Ability System (Editor)

Niagara VFX (Editor)

Mesh Generation (Editor)

Levels (Editor)

Editor Utilities (Editor)

Components & Instancing (Editor)

Textures (Editor)

DataTables (Editor)

Fab Marketplace (Editor)

Subsystems & UI (Editor)

Network Debug (Editor)

Documentation (Always Available)

Documentation Index

Build the local documentation search index:

mcp-unreal --build-index

This indexes markdown files from docs/ue5.7/ and docs/realtimemesh/, plus your project's CLAUDE.md. The index is stored at ./docs/index.bleve (configurable via MCP_UNREAL_DOCS_INDEX).

To add custom documentation, place markdown files in the docs/ directory and rebuild the index. See docs/README.md.

Example Usage

Once registered, your AI agent can autonomously:

You: "Build the project, fix any errors, and run the tests"

Agent calls:
  1. status()                    → editor + plugin online
  2. build_project()             → finds 2 compile errors
  3. lookup_class("AActor")      → looks up the correct API
  4. (edits the C++ source)
  5. build_project()             → clean build
  6. run_tests(filter: "Game")   → 14/14 tests pass

You: "Add a Niagara fire effect to the torch actor"

Agent calls:
  1. get_level_actors(name_filter: "Torch")  → finds actor path
  2. lookup_class("UNiagaraComponent")       → checks API
  3. niagara_ops(operation: "spawn_system", system_path: "/Game/FX/NS_Fire", ...)
  4. niagara_ops(operation: "set_parameter", parameter_name: "SpawnRate", value: 50)

You: "Create a PCG scatter for placing rocks on the landscape"

Agent calls:
  1. lookup_docs("PCG scatter landscape")    → reads PCG docs
  2. pcg_ops(operation: "list_components")   → finds existing PCG actors
  3. spawn_actor(class: "Actor", name: "RockScatter")
  4. pcg_ops(operation: "add_node", node_type: "SurfaceSampler")
  5. pcg_ops(operation: "execute")           → generates rocks

Development

# Build
make build

# Run all tests with race detector
make test

# Go lint
make lint

# C++ format check (requires clang-format)
make cpp-fmt-check

# Run all checks (Go format, C++ format, vet, lint, tests)
make check

C++ Plugin Tests

The MCPUnreal plugin includes automation tests that run inside the UE editor headlessly. These require UE 5.7 installed locally and are not part of CI — they are opt-in for local development.

# Build the test project (first run ~2-5 min, incremental after)
make test-cpp-build

# Build and run all MCPUnreal.* automation tests
make test-cpp

This uses a minimal UE project in test-project/ that symlinks the plugin source and runs all MCPUnreal.* tests via UnrealEditor-Cmd -nullrhi.

Contributing

See CONTRIBUTING.md for development setup, coding standards, and how to add new tools.

License

Apache-2.0 — see LICENSE.

Unreal Engine is a trademark of Epic Games, Inc. This project is not affiliated with or endorsed by Epic Games.