draw.io + MCP vs Kroki

draw.io + MCP

Free, keyless and Apache 2.0, with a Docker image for self-hosting. Tool descriptions embed a 34.5 KB XML reference and a 14 KB Mermaid reference, roughly 13,000 tokens.

Kroki

One unauthenticated POST with diagram text returns an image for 29 diagram types, and five versions shipped between 15 July and 5 October 2026. Four advisories were published in July and August 2026, one an unauthenticated remote code execution on /tikz/svg, all fixed. No OpenAPI file exists, and the public instance has no terms, privacy policy or status page.

draw.io + MCP

1. Pass mermaid to create_diagram for any type on its Mermaid list. Use xml only for icons, mockups or hand-placed layouts
2. Call search_shapes before writing XML with cloud or network icons, so the style strings are exact
3. Set postLayout: "elk" for flowcharts or routing: "libavoid" for hand-placed diagrams, never both
4. Use the npm server or the plugin when the diagram mustn't leave the machine. The hosted App sends it to draw.io's server
5. Expect the tool list to cost about 13,000 tokens before the first call

Kroki

1. Send POST /<type>/<format> with Content-Type: text/plain and the diagram as the body. This avoids the deflate and base64 encoding that GET needs
2. Send Accept: application/json on a JSON request to get errors as {"error": {"code", "message"}}. With an SVG Accept header the error arrives as an image
3. Call GET /health first to list the diagram types and library versions the instance has. Mermaid, BPMN, Excalidraw and diagrams.net need companion containers
4. Run 0.32.1 or later before rendering untrusted text. Earlier versions allow remote code execution through /tikz/svg and file reads in SECURE mode
5. Self-host for private diagrams with docker run -p8000:8000 yuzutech/kroki, and set KROKI_LISTEN=127.0.0.1:8000 or a network rule, since the server has no authentication