marvelous-designer-mcp

A Model Context Protocol server that lets an LLM (e.g. Claude) drive Marvelous Designer (and CLO, which shares the same Python API) by running code inside MD’s embedded Python interpreter.

It does not need the C++ SDK, a plugin build, or a CLO-SET API key — just MD’s built-in Python Editor.

How it works

LLM  ──MCP(stdio)──▶  MCP server (this repo, FastMCP)
                          │  JSON-per-line over TCP 127.0.0.1:7421
                          ▼
                      md_listener.py  (you paste it into MD's Python Editor)
                          │  exec() in MD's interpreter
                          ▼
                      MD Python API:  import_api / export_api / fabric_api /
                                      pattern_api / utility_api / ...

MD’s embedded Python (3.11) does not schedule background threads, so the listener is a plain blocking accept loop that runs on MD’s GUI thread. While the listener is running, MD’s window is unresponsive — that’s expected. Stop it with the shutdown_listener tool (or by closing MD).

Requirements

• Marvelous Designer 2026 (or CLO 2026) — Plugins ▸ Python Editor must be available
• Python 3.10+ and uv on the machine running the MCP server
• The MCP server and MD run on the same machine (the listener binds 127.0.0.1)

Setup

git clone https://github.com/ysk424/marvelous-designer-mcp.git
cd marvelous-designer-mcp
uv sync

Running

1. Start the listener inside Marvelous Designer

scripts/md_start_listener.py starts a blocking socket listener on 127.0.0.1:7421. MD’s GUI freezes while it runs — that’s the ready state. Stop it later with the shutdown_listener tool (or by closing MD). See Why does MD freeze? below.

Option C — auto-register (one shot, recommended). Run

uv run python scripts/install_md_plugin.py

once. It writes the launcher into MD’s pluginSettings.json, so on the next MD launch Plugins ▸ Plug-in ▸ md_start_listener is there waiting to be clicked.

Option B — register manually. Plugins ▸ Plug-in Manager ▸ +ADD, pick scripts/md_start_listener.py. Same outcome as Option C, just hand-driven.

Option A — paste into the Python Editor. Open Plugins ▸ Python Editor, paste the whole contents of scripts/md_start_listener.py, run it. (Paste it in one go from a text editor — pasting line by line can mangle indentation.) Good for development; the editor’s console shows prints.

Either way, status and errors are appended to ~\md_mcp_listener.log (handy in plugin mode, where stdout may not be visible).

2. Start the MCP server

uv run python -m marvelous_designer_mcp

Or let Claude Desktop launch it (below).

3. Claude Desktop config

Add to claude_desktop_config.json