Excalidraw Skill

Step 0: Pick an Interface

Three interfaces drive the same live canvas. Pick the first one that applies:

1. MCP tools — if excalidraw/* tools (e.g. batch_create_elements) are in your tool list, prefer them: results land directly in your context, and screenshots come back as images without touching disk.
2. CLI (default when no MCP tools are present):

   npx -y mcp-excalidraw-server <command>
   

   No setup needed — any canvas-touching command auto-starts the canvas server on http://127.0.0.1:3000 (first npx run downloads the package). If the CLI is installed globally (npm i -g mcp-excalidraw-server), the shorter alias excalidraw-canvas <command> works too.
3. REST API (last resort, e.g. from application code): HTTP endpoints on http://127.0.0.1:3000 — see references/cheatsheet.md for payloads. The server must already be running.

The canvas URL comes from EXPRESS_SERVER_URL (default http://127.0.0.1:3000). Remind the user to open that URL in a browser — screenshots, image export, mermaid conversion, and viewport control need an open tab (CLI exits with code 4 when it's missing).

CLI Quick Reference

Results are JSON on stdout — except describe (plain text) and raw-content output when --out is omitted (export scene JSON, screenshot --format svg). Diagnostics on stderr. Exit codes: 0 ok, 1 error, 2 usage, 3 canvas unreachable, 4 browser tab required.