UML Forge — MCP Connector

13 AI-powered UML diagram tools for Claude Code, Cursor, Windsurf, and any MCP-compatible coding agent.

What is this?

This repository contains the open-source MCP connector for UML Forge — a hosted service that generates professional Mermaid UML diagrams from inside your coding environment.

When installed, the connector runs locally as a stdio MCP server. Your coding agent (Claude Code, Cursor, Windsurf, etc.) calls one of the 13 diagram tools, the connector forwards the request to the UML Forge API (api.umlforge.dev), and the diagram is returned directly in your editor.

Your editor  →  MCP connector (this repo, runs locally)  →  UML Forge API  →  Mermaid diagram

No code is stored. Input is processed in memory on the API server and discarded after the response is returned. See Security and Privacy below.

Quick start

1. Get an API key

Sign up for a free account at umlforge.dev. The free tier includes 5 diagrams per month with no credit card required.

2. Configure your editor

Claude Code — add to .mcp.json in your project root:

{
  "mcpServers": {
    "umlforge": {
      "command": "uvx",
      "args": ["umlforge==0.1.1"],
      "env": {
        "UMLFORGE_API_KEY": "your-api-key-here"
      }
    }
  }
}

Cursor — add to your MCP settings (~/.cursor/mcp.json or the project .cursor/mcp.json):

{
  "mcpServers": {
    "umlforge": {
      "command": "uvx",
      "args": ["umlforge==0.1.1"],
      "env": {
        "UMLFORGE_API_KEY": "your-api-key-here"
      }
    }
  }
}

Windsurf — same JSON block, placed in your Windsurf MCP configuration.

Tip: Pin the version (umlforge==0.1.1) so your setup is reproducible. Check PyPI for the latest release.

Tools included

How it works

This connector is intentionally thin. Every tool in connector/tools.py does one thing: forward the call to the UML Forge API.

api_client.py sends an authenticated HTTPS POST to https://api.umlforge.dev/v1/generate with:

• The tool name
• Your input (code snippet, description, GitHub URL, etc.)
• Your API key in the Authorization: Bearer header

The API server runs the diagram generation, validates the Mermaid output, and returns it. The connector passes the result back to your editor.

There is no local LLM, no file system access, no process spawning, and no data persistence in the connector.

Security and privacy

What is sent to the API:

• Your tool inputs (code snippets, system descriptions, GitHub URLs you explicitly provide)
• Your API key (used for authentication and rate limiting only)

What is NOT collected:

• File system contents beyond what you explicitly pass to a tool
• Environment variables or secrets
• Conversation history from your editor
• Any data beyond the specific tool call arguments

API server behaviour:

• Input is processed in memory and discarded after the response is returned
• No code or description you submit is stored
• All traffic is encrypted via TLS (HTTPS)

Full privacy policy: umlforge.dev/privacy

Requirements

• Python 3.11 or later
• uvx (comes with uv) — or install with pip install umlforge
• An API key from umlforge.dev

Repository structure

connector/
  __init__.py       — package marker
  __main__.py       — entry point for uvx umlforge
  server.py         — FastMCP server initialisation
  tools.py          — 13 MCP tool definitions (signatures + docstrings)
  api_client.py     — HTTPS client for api.umlforge.dev
  config.py         — API key loading from UMLFORGE_API_KEY env var
  README.md         — PyPI package description
pyproject.toml      — package metadata and dependencies
server.json         — MCP Registry metadata

The diagram generation logic, prompt engineering, Mermaid validation, and billing are all server-side at api.umlforge.dev and are not part of this repository.

License

The connector is proprietary software. It is freely distributable and installable for use with a UML Forge account. Redistribution or modification without permission is not permitted.

© 2026 UML Forge. All rights reserved.

Links

• Website: umlforge.dev
• PyPI: pypi.org/project/umlforge
• MCP Registry: registry.modelcontextprotocol.io
• Support: [email protected]