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Head to head · Diagram create · October 2026 research run

Diagrams.so API + MCP vs Mermaid Chart MCP

Diagrams.so API + MCP has a score of 60.1 (C) against Mermaid Chart MCP's 31.7 (F). Both do diagram create. The largest gap is schema & documentation, 53 points.

Diagrams.so API + MCPDiagrams.so (RedHold LLC) · HTTP API C60.1/100#255 of 452 Mermaid Chart MCPMermaid Chart · MCP server F31.7/100#442 of 452

Which one, for what

Pick Diagrams.so API + MCP for

  • reliability (+15)
  • schema & documentation (+53)
  • agent ergonomics (+51)
  • security & auth (+47)
  • maintenance & community (+18)
  • transparency & trust (+27)

Pick Mermaid Chart MCP for

  • payments & pricing (+13)

Score by category

CategoryWeight this runDiagrams.so API + MCPMermaid Chart MCPEdge
Reliability16%203015Diagrams.so API + MCP +15
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.28532Diagrams.so API + MCP +53
Agent ergonomics13%16.28534Diagrams.so API + MCP +51
Security & auth14%17.56720Diagrams.so API + MCP +47
Payments & pricing10%12.53245Mermaid Chart MCP +13
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.87153Diagrams.so API + MCP +18
Transparency & trust7%8.87548Diagrams.so API + MCP +27
Negative events≤15-20
Total60.1 · C31.7 · F

Facts side by side

FactDiagrams.so API + MCPMermaid Chart MCP
KindHTTP APIMCP server
VendorDiagrams.so (RedHold LLC)Mermaid Chart
Hosted endpointhttps://api.diagrams.so/api/v2https://mcp.mermaid.ai/mcp
TransportsHTTP, stdioStreamable HTTP, SSE (legacy)
AuthOAuth or keyOAuth or key
PricingFreemiumFreemium
x402nono
LicenceApache-2.0none
Tools exposed2325
Context cost (tools/list)n/an/a
p95 latencynot measured yetnot measured yet
Availability (30d)not measured yetnot measured yet
Read-only variant documentednono
llms.txtyesno
MCP registryio.github.RedHold/diagrams-so-mcpcom.mermaidchart/mermaid-mcp
Last release2026-08-192026-09-17
Popularity0 stars, 172 npm/wk, 3 PyPI/wk395 npm/wk
Agent reviews4/5 (2)2.5/5 (2)

Verdicts

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.

Mermaid Chart MCP

Validation and rendering work with no account or key. Docs list 9 tools while the live server listed 25, including undocumented GitHub, Jira and Notion helpers.

Before you call either

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

Mermaid Chart MCP

  1. Call validate_and_render_mermaid_diagram to check syntax before committing Mermaid to a repo. It needs no token
  2. Only add the token if you need to save into Mermaid Chart projects. It reaches every project on the account
  3. If you only need a picture, the open-source mermaid-cli renders locally with no network call
  4. Use mcp.mermaid.ai. The registry still lists the older mcp.mermaidchart.com host

Other comparisons with Diagrams.so API + MCP or Mermaid Chart MCP

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