Self-hosted Excalidraw app adds MCP so Claude can draw diagrams and read them back
KindlyLeadership7978 · reddit · 2026-11-06
The developer of Excaliself, a self-hosted whiteboard app built around Excalidraw (MIT, Postgres, live collab), added an MCP server that lets Claude Code draw a web app architecture from one prompt and read the drawing back. Key design details: 11 tools for listing/searching/reading/creating drawings; readdrawing returns a concise text description of shapes, labels and connections instead of raw JSON to save tokens; createdrawing auto-layouts plain shapes or accepts Mermaid; OAuth with dynamic client registration and PKCE for Claude.ai compatibility (which can't send custom headers), via Streamable HTTP with a public HTTPS requirement. A one-line Docker command runs a throwaway stdio preview. Next up: Claude editing existing drawings with on-canvas user approval.
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