MCPBridge Server

Companion MCP server for the MCP Bridge Unreal Engine 4.27 editor plugin. It translates Model Context Protocol tool calls from AI coding agents (Claude Code, Codex, Cursor, or any MCP client) into HTTP commands for the listener that the plugin runs inside the Unreal editor.

AI agent (MCP client) --stdio--> this server --HTTP localhost:8080--> UE4.27 editor (MCP Bridge plugin)

All communication stays on your machine: the server talks only to localhost:8080, where the plugin's in-editor listener accepts connections from the local machine only.

Requirements

• Node.js 18 or newer
• The MCP Bridge plugin installed and enabled in a UE 4.27 project (available on Fab; the plugin's Quick Start covers editor setup)

Setup

npm install
npm run build

Then register the server with your MCP client. For Claude Code, add this to your project's .mcp.json (adjust the path to where you cloned this repo):

{
  "mcpServers": {
    "unreal-bridge": {
      "command": "node",
      "args": ["<path-to-this-repo>/dist/index.js"]
    }
  }
}

Start your UE 4.27 project with the plugin enabled, then ask your agent to run test_connection. A healthy reply includes the engine version and project paths.

What the tools cover

150+ tools across: actor and level editing, Blueprint creation and compilation, Blueprint member/graph editing with schema-validated pin connections, gameplay framework generation (GameMode/Character/controller/HUD with class defaults wired), input mappings and control-scheme presets, camera rig presets, Blackboards and Behavior Trees built from JSON, C++ class generation and UnrealBuildTool compilation as background jobs with structured error reporting, materials and material instances, DataTables, audio components, map creation, viewport control and screenshots, and a searchable project intelligence index.

Every editor mutation runs in a UE4 transaction (undo works), compiles and saves the affected asset, and reports failure explicitly - a broken Blueprint is never reported as success.

Tests

npm test              # unit tests against a mock listener; no Unreal needed
npm run test:integration  # requires UE 4.27 running with the plugin listener

The registry-consistency test cross-checks this server's tools against the plugin's Python command router; it runs in the plugin's development repository and skips automatically here.

Versioning

Server and plugin versions track each other (this is v0.4.0, matching plugin v0.4.0). When updating one, update the other.

License

MIT - see LICENSE.