d2-mcp-server

An MCP (Model Context Protocol) server for the D2 diagram language. Lets LLMs render, validate, and format D2 diagrams without requiring the d2 binary — rendering is powered by the @terrastruct/d2 WASM package.

Tools

Related MCP server: mcp-mermaid-validator

Install the D2 Skill

The repo ships a d2 agent skill that teaches LLMs how to write effective D2 diagrams (syntax, styling, patterns, when to use which layout engine, and how to save output).

Install it via skills.sh:

npx skills add itsjool/d2-mcp

This drops skills/d2/SKILL.md into your agent's skills directory so it's automatically available in any session.

Requirements

• Node.js 18+

• d2 binary only required for d2_format — install from d2lang.com or set D2_PATH env var

Install

npm install
npm run build

Usage with Claude Code

Via npx (no install required):

{
  "mcpServers": {
    "d2": {
      "command": "npx",
      "args": ["-y", "github:itsjool/d2-mcp"]
    }
  }
}

Via local build:

{
  "mcpServers": {
    "d2": {
      "command": "node",
      "args": ["/path/to/d2-mcp/dist/index.js"]
    }
  }
}

Then start Claude Code with:

claude --mcp-config /path/to/mcp.json

Development

npm run dev     # watch mode with tsx
npm run build   # compile TypeScript to dist/
npm start       # run compiled server

Notes

• ELK layout is significantly slower than dagre in WASM; prefer dagre unless you specifically need ancestor-to-descendant connections or container sizing

License

MIT