Quick Start

By the end of this page an AI agent (Claude Code, Cursor, VS Code, Gemini, or Codex) will be able to call Crimson's MCP tools against your open project - reading source, listing plugins, and inspecting assets - through the editor's built-in MCP server.

Prerequisites
A UE 5.8 project with CrimsonEditorUtilities enabled (Edit -> Plugins), and an MCP-capable AI client installed on your machine. The ModelContextProtocol and ToolsetRegistry engine plugins are pulled in automatically by this plugin.

1. Enable Crimson MCP

Open Project Settings -> Crimson -> Crimson MCP and tick Enable Crimson MCP, then restart the editor. The flag is read at module startup, so the restart is what actually registers the toolsets. (You can also flip this from the Crimson MCP toolbar button - see How-To: Manage MCP Toolsets.)

Screenshot pendingImages/CrimsonEditorUtilities/qs-enable-mcp.png
Project Settings -> Crimson -> Crimson MCP -> tick 'Enable Crimson MCP', then restart the editor.
Verify
After the restart, the three Crimson toolsets are registered. You will confirm them from the agent in step 3.

2. Start the MCP server

The server is off until you start it. Open Editor Preferences -> Model Context Protocol and tick Auto Start Server (or run the console command ModelContextProtocol.StartServer). It binds to http://127.0.0.1:8000/mcp by default - loopback only.

Verify
The Output Log prints the MCP bind address on startup. Raise detail with Log LogModelContextProtocol Verbose if you need it.

3. Point your AI client at the server

Generate a client config from the console, then launch the agent from your project root:

text
ModelContextProtocol.GenerateClientConfig ClaudeCode

Supported client arguments are ClaudeCode, Cursor, VSCode, Gemini, Codex, or All. This writes the client's MCP config file (for Claude Code, .mcp.json in the project root).

Verify
In the agent, list toolsets (the list_toolsets meta-tool). You should see CrimsonSourceToolset, CrimsonPluginToolset, and CrimsonAssetToolset. Ask it to read a file - e.g. call ReadFile with Config/DefaultEngine.ini - and confirm it returns the contents.
Local machine only
The MCP server binds to loopback and has no authentication. It is meant for your own editor on your own machine - never expose the port to a network.
What's next
Choose which toolsets agents can see - including Epic's own (GAS, Gameplay Tags, Editor) - with How-To: Manage MCP Toolsets. Learn the model behind it in Concept: How Crimson MCP Works.