Miro API + MCP vs pen.dev

Miro API + MCP

REST creates shapes, connectors and frames, so flowcharts and architecture sketches can be drawn directly. Legacy MCP board tools were removed nine days after the deprecation notice.

pen.dev

An agent can create, edit and export .pen designs without a GUI through the pen CLI, with four compact MCP tools that carry annotations and a documented JSON format. The software is closed and needs a pen.dev account. No changelog, status page or security contact was found, and 14 public issue reports had no reply on 8 October 2026.

Miro API + MCP

1. Create shapes first, then connectors with startItem and endItem ids
2. Put related items in a frame and set parent so they move together
3. Watch X-RateLimit-Remaining. There's no Retry-After, so back off exponentially on 429
4. Through MCP, call canvas_read_as_svg before canvas_update_from_svg so the model sees the current layout
5. Don't call the legacy MCP board tools. They were removed on 17 September 2026

pen.dev

1. Call read_skill(), then read_skill({ path: "pen-schema.md" }) and read_skill({ path: "execute.md" }) before the first execute. The tool description alone doesn't document the operations
2. Call get_app_state() and confirm the active document before editing. The MCP server works on whichever .pen file is open in the app
3. In headless pen interactive, call save() before exit(), and keep --in and --out on different paths to preserve the source
4. Check that an export file exists. The docs say an export failure can print an error without a nonzero exit status
5. In CI set PEN_CLI_KEY plus a provider key such as ANTHROPIC_API_KEY. Run pen version, since pen --version is not a flag