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Documentation Index

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What is Unreal MCP Web Client?

Unreal MCP Web Client is an interactive single-page application (SPA) designed to debug and consume the built-in MCP server that ships with Unreal Engine 5.8. It lets you graphically inspect active toolsets, explore their JSON-RPC argument schemas, make real-time tool calls, and read progressive responses delivered over Server-Sent Events (SSE). The project is made up of four tightly integrated components that work together to put AI agents in control of the Unreal Editor:
ComponentRole
Web client (index.html + src/js/app.js)Browser-based SPA — 5-panel UI for connecting, exploring toolsets, and executing tools
server.pyFastAPI proxy on port 5000 — forwards requests to Unreal’s MCP server at http://localhost:8000/mcp, handles CORS, flattens toolsets, and caches tool schemas
bridge.pystdio-to-HTTP-SSE bridge — translates Claude Desktop’s JSON-RPC stdio protocol into direct HTTP calls to Unreal’s MCP server on port 8000
dbv-unreal-python-api skillLocal knowledge base of the full Unreal Engine 5.8 Python API and conceptual development guides, exposed as searchable MCP tools for AI agents

How it connects

Unreal Engine 5.8 ships with a built-in MCP server that listens on http://localhost:8000/mcp. The proxy (server.py) sits in front of it, adding CORS headers, intercepting tools/list to flatten the nested toolset hierarchy into a single list, and caching tool schemas so subsequent fetches are near-instant.
Browser / Gemini Agent


 server.py  :5000   ←─ FastAPI proxy + toolset cache


Unreal Engine MCP  :8000/mcp   ←─ built-in MCP server
For Claude Desktop or Claude Code, bridge.py bypasses the proxy entirely and speaks directly to Unreal’s MCP server over stdio, translating the MCP protocol line-by-line.

Two Ways to Use It

1 — Web browser with Gemini AI agent

Open http://localhost:5000 after running start.sh / start.cmd. The SPA connects to the FastAPI proxy, fetches your toolsets, and can forward multi-turn Gemini agent conversations to the Unreal editor in real time.

2 — Claude Desktop or Claude Code via bridge.py

Register bridge.py as a stdio MCP server in your claude_desktop_config.json. Claude will discover all Unreal toolsets and call editor tools without any browser involved.

Key Features

SSE Streaming

Real-time progressive responses from Unreal streamed over Server-Sent Events — no polling, no timeouts.

Toolset Discovery & Caching

Automatically enumerates all registered toolsets and caches their JSON schemas to disk. Re-fetches only when the toolset list changes.

Namespace Translation

Automatically maps short toolset names like SceneTools to their full internal class path (e.g. editor_toolset.toolsets.scene.SceneTools).

Gemini Multi-Turn Agent

Built-in Gemini agent integration in the web client for multi-step, context-aware automation across the Unreal Editor.

Python API Knowledge Base

Searchable local index of 11,000+ Unreal Engine 5.8 Python API pages — class signatures, method names, and parameters — so agents generate correct scripts without hallucinations.

Cloudflare-Bypass Documentation Crawler

Playwright-powered crawler opens a real Chromium context per page to bypass Cloudflare Bot Management and download Epic’s full conceptual documentation locally.

Explore the Docs

Quickstart

Install dependencies, start the proxy, and make your first tool call in under five minutes.

Web Client Overview

Understand the five-panel UI, SSE stream decoder, and Gemini agent integration.

Unreal Integration

Enable the required plugins, wire up the MCP server, and create custom toolsets.

Claude Desktop Setup

Register bridge.py as a stdio MCP server so Claude Desktop can call Unreal tools directly.

Python API Skill

Learn how the dbv-unreal-python-api skill powers accurate Python script generation for AI agents.

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