Diagrams.so API + MCP vs Kroki

Diagrams.so API + MCP

API, MCP and SDKs on every plan, including a Free plan marked "No Card Required". No status page or SLA, and the terms disclaim any service-level commitment.

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.

Diagrams.so API + MCP

1. Send an Idempotency-Key on generate, edit, fix and re-layout. If a billable call times out, check get_usage_history before retrying
2. Generation is synchronous and can run for minutes. The SDKs default to a 450 s timeout, or use POST /diagrams/stream
3. Call list_capabilities first. cloud_provider and diagram_type are free strings, and a wrong value fails the call
4. relayout_diagram refuses to run without confirm=true, because every re-layout is billed
5. Test keys (dgz_test_) spend the same credits as live keys

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