agentcraft-mcp

Hybrid MCP server for Unreal Engine 5 — runs as an independent Node.js process and bridges to the AgentCraft (KaiWu) editor plugin over WebSocket. Offline tools work without UE.

What this is

agentcraft-mcp is the standalone npm distribution of the MCP (Model Context Protocol) server that ships with AgentCraft / KaiWu, an AI-driven editor plugin for Unreal Engine 5.

It speaks MCP spec 2025-11-25 and exposes two kinds of tools:

1. Offline tools — pure Node.js, no UE required. File system navigation, INI reading, C++ source search, project info, notifications. Useful from any MCP client (Claude Desktop, VS Code, Cursor, OpenCode, Codex, etc.).
2. UE-attached tools — proxied to a running UE 5 editor with the AgentCraft plugin loaded (HTTP :9316 direct, or WebSocket bridge :9877 for hybrid mode). 271 tools across Blueprint, Material, PCG, Spline, Animation, Niagara, Level Actor, Sequencer, etc.

Install

npm install -g agentcraft-mcp

Two CLI entries are installed:

| Command | Use | |---|---| | agentcraft-mcp | Main hybrid MCP server (offline + WebSocket-to-UE) | | agentcraft-mcp-bridge | stdio↔HTTP bridge for clients that only speak stdio (legacy UE-attached mode) |

Quick start

Standalone (no UE required)

agentcraft-mcp --profile generic

Then point any MCP client at the stdio entry. Sample configs are in configs/ for:

• Claude Desktop
• VS Code (native MCP)
• OpenCode

UE-attached (with AgentCraft editor plugin running)

Start UE 5.7 editor with the AgentCraft plugin enabled, then point your MCP client at the stdio bridge:

agentcraft-mcp-bridge   # bridges stdio ↔ http://127.0.0.1:9316/mcp

Sample configs:

• Claude Desktop
• VS Code (native MCP)
• OpenCode

HTTP transport (network-exposed)

agentcraft-mcp --transport http --http-host 0.0.0.0 --http-port 9316 \
               --api-key $AC_MCP_API_KEY --cors-origin '*'

Docker

Multi-arch images on ghcr.io:

docker run --rm -p 9316:9316 ghcr.io/mullin2012/agentcraft-mcp:latest

Tool surface

| Profile | Tool count | Description | |---|---|---| | generic | ~14 | Offline only (file system, INI, C++ source, project info) | | ue | 285+ | Full catalogue (offline + UE-attached via WebSocket bridge) |

Run npx --yes @modelcontextprotocol/inspector --cli stdio agentcraft-mcp --method tools/list to see the active list for your environment.

Security

| Feature | Default | Override | |---|---|---| | Bearer auth | off | --api-key <token> or AC_MCP_API_KEY=<token> | | CORS | restrictive | --cors-origin '<origin>' | | Body size limit | 1 MiB | hard-coded; 413 on overflow | | Session timeout | 30 min idle | hard-coded; 60 s cleanup interval | | Graceful shutdown | enabled | 5 s drain |

/health is always auth-exempt for container probes.

Architecture

MCP Client (Claude Desktop / VS Code / Cursor / Codex / OpenCode / Inspector)
    ↓ stdio  or  HTTP
agentcraft-mcp  (this package, node process)
    ├─ Offline tools  →  Node.js fs / parsers
    ├─ stdio bridge   →  HTTP /mcp on running UE editor :9316
    └─ WebSocket bridge :9877 ─→ UE editor (AgentCraft plugin)
                                 └─ FCraftToolRegistry → kaiwu_* tools

Related projects

• AgentCraft / KaiWu — the UE 5 editor plugin that originated this MCP server
• Model Context Protocol — the open spec this server implements

License

MIT. See LICENSE.

Contributing

Issues and PRs welcome at github.com/mullin2012/agentcraft-mcp.

Provenance

This package was extracted from the AgentCraft monorepo at 2026-05-27 as part of the Phase E / Round 26 architectural split. See CHANGELOG.md for details.