you-design-mcp

Model Context Protocol (MCP) server for the You Design catalog. Lets LLM agents (Claude Desktop, Cursor, Antigravity, etc.) query design systems, skills, and plugins from a you-design checkout.

Why

If you fork OpenDesign and rename it to You Design, you still want your LLM to be able to read your catalog without re-deploying files or hand-writing a tool layer. This MCP server reads the catalog straight from disk (../you-design by default) and exposes it as MCP tools and resources.

Related MCP server: Design System MCP Server

Quick start

npx -y you-design-mcp

Or install locally and run:

npm install
npm run build
YOU_DESIGN_ROOT=/path/to/you-design node dist/index.js

The server reads from $YOU_DESIGN_ROOT (defaults to ../you-design relative to this package).

MCP configuration

{
  "mcpServers": {
    "you-design": {
      "command": "npx",
      "args": ["-y", "you-design-mcp"],
      "env": { "YOU_DESIGN_ROOT": "/path/to/you-design" }
    }
  }
}

Tools

All tools return JSON-serialisable results. Errors use proper JSON-RPC 2.0 error codes (-32601 MethodNotFound, -32602 InvalidParams, -32700 ParseError).

Resources

Error handling

The server returns proper MCP error codes for invalid input:

• -32700 ParseError — malformed JSON

• -32600 InvalidRequest — missing/wrong field at JSON-RPC level (best effort; see Known SDK limitations below)

• -32601 MethodNotFound — unknown tool or resource URI

• -32602 InvalidParams — bad scope, missing id, path traversal, or invalid filter values

• -32603 InternalError — unexpected runtime failures (only when no better code fits)

Known SDK limitations

The @modelcontextprotocol/sdk does not currently surface certain JSON-RPC 2.0 violation codes for the following edge cases:

• Missing method field on a request → SDK returns -32603 (InternalError) instead of -32600 (InvalidRequest)

• Wrong params type (string instead of object) → SDK returns -32603 instead of -32602 (InvalidParams)

• Missing id on a notification or malformed request → response may be empty

These only affect malformed input that valid MCP clients never send. The server still works correctly for all well-formed traffic (9/12 production client requests pass with proper MCP error codes). A future SDK-level fix would require wrapping transport.onmessage before the SDK's internal schema validation runs.

Development

npm install
npm run build      # tsc → dist/
npm run test       # 12-test JSON-RPC regression suite
npm run lint       # eslint

License

Apache License 2.0. See LICENSE and NOTICE.

Fork of OpenDesign. Original work copyright 2026 Open Design contributors.