design-canvas-mcp

MCP server for Design Canvas — control the infinite canvas from AI coding agents.

Design Canvas is a native Mac app that shows all your web app's routes on an infinite canvas with live browser views. This MCP server lets AI agents (Claude Code, Cursor) add routes, capture screenshots, and manage what's displayed.

Prerequisites

• Design Canvas Mac app must be running on your machine
• The app must be connected to a running dev server (e.g., localhost:3000)
• Node.js 20+

Installation

Claude Code

claude mcp add design-canvas -s user -- npx -y design-canvas-mcp

Cursor

Add to .cursor/mcp.json:

{
  "mcpServers": {
    "design-canvas": {
      "command": "npx",
      "args": ["-y", "design-canvas-mcp"]
    }
  }
}

Global install (alternative)

npm install -g design-canvas-mcp

Then configure with command: "design-canvas-mcp" instead of the npx variant.

Tools

Tool	Description	Key Parameters
list_routes	List all routes on the canvas with IDs, paths, dimensions, positions	—
add_route	Add a route to the canvas from the connected dev server	path (required), width (1280/768/375)
remove_route	Remove a route frame by ID or path	id (preferred) or path
capture_canvas	Capture screenshots of routes and return as images	ids (optional), limit (default: 3)

Example prompts

• "Show me all routes on the canvas" → list_routes
• "Add /dashboard at desktop and mobile" → add_route at 1280 + 375
• "Capture the canvas so you can see my app" → capture_canvas
• "Remove the mobile version of /dashboard" → list_routes then remove_route by ID

How it works

The MCP server communicates with the Design Canvas Mac app via a local HTTP API on localhost:7420. The server is an adapter layer — it translates between the HTTP API and MCP's content block format.

Claude Code / Cursor
    → spawns design-canvas-mcp (stdio)
        → HTTP requests to localhost:7420
            → Design Canvas Mac app responds

Screenshots are captured by the Mac app's WebKit rendering engine, resized to 1200px width, and returned as base64 JPEG images.

Troubleshooting

"Design Canvas is not running" The Mac app isn't open or isn't listening on port 7420. Open Design Canvas and make sure it shows the canvas view.

Routes show but pages are blank The dev server isn't running. Start your dev server (e.g., npm run dev) and make sure Design Canvas is connected to it.

Screenshots are from WebKit, not Chrome Design Canvas uses WebKit (Safari's engine) for rendering. For pixel-perfect Chromium verification, use Playwright. The MCP screenshots are for quick layout checks, not cross-browser QA.

License

MIT