d2-mcp

MCP server for the D2 diagram language. Compile, validate, and explore D2 diagrams from any MCP-compatible AI assistant.

Uses the native D2 CLI binary (installed automatically in the Docker image) to compile diagrams into SVG and PNG.

Tools

Resources

Local Development

Prerequisites

• Node.js 22+

• D2 CLI — install from d2lang.com or set the D2_PATH env var to the binary location.

• Icons (optional) — run scripts/download-icons.sh ./icons then set ICONS_DIR=./icons to enable local icon resolution. Without this, icon URLs are passed through to the D2 CLI as-is.

npm install
npm run build
npm start

For development with auto-reload:

npm run dev

The server starts on port 3000 by default (override with PORT env var).

• Health check: GET /health

• MCP endpoint: POST /mcp (Streamable HTTP transport)

Environment Variables

Deployment (Render)

This project includes a Dockerfile and render.yaml blueprint for one-click deployment to Render. The Docker image automatically installs the D2 CLI binary and downloads all icons at build time.

1. Push this repo to GitHub

2. In Render, create a new Blueprint and connect your repo

3. Render will auto-detect render.yaml and deploy

Or manually create a Web Service with:

• Environment: Docker

• Health Check Path: /health

• Plan: Free

Connecting to the MCP Server

Once deployed, configure your MCP client to connect via Streamable HTTP:

{
  "mcpServers": {
    "d2": {
      "url": "https://your-service.onrender.com/mcp"
    }
  }
}

Replace the URL with your actual Render service URL (or http://localhost:3000/mcp for local).

Compile Tool Options

License

MIT