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Head to head · Diagram create · October 2026 research run

Diagrams.so API + MCP vs Structurizr + MCP

Structurizr + MCP has a score of 60.2 (C) against Diagrams.so API + MCP's 60.1 (C). Both do diagram create. The largest gap is reliability, 43 points.

Diagrams.so API + MCPDiagrams.so (RedHold LLC) · HTTP API C60.1/100#255 of 452 Structurizr + MCPStructurizr · HTTP API C60.2/100#252 of 452

Which one, for what

Pick Diagrams.so API + MCP for

  • schema & documentation (+24)
  • agent ergonomics (+30)
  • security & auth (+24)

Pick Structurizr + MCP for

  • reliability (+43)
  • payments & pricing (+18)
  • transparency & trust (+5)

Score by category

CategoryWeight this runDiagrams.so API + MCPStructurizr + MCPEdge
Reliability16%203073Structurizr + MCP +43
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.28561Diagrams.so API + MCP +24
Agent ergonomics13%16.28555Diagrams.so API + MCP +30
Security & auth14%17.56743Diagrams.so API + MCP +24
Payments & pricing10%12.53250Structurizr + MCP +18
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.87168Diagrams.so API + MCP +3
Transparency & trust7%8.87580Structurizr + MCP +5
Negative events≤15-20
Total60.1 · C60.2 · C

Facts side by side

FactDiagrams.so API + MCPStructurizr + MCP
KindHTTP APIHTTP API
VendorDiagrams.so (RedHold LLC)Structurizr
Hosted endpointhttps://api.diagrams.so/api/v2https://mcp.structurizr.com/mcp
TransportsHTTP, stdioHTTP, Streamable HTTP
AuthOAuth or keyOAuth or key
PricingFreemiumFreemium
x402nono
LicenceApache-2.0Apache-2.0
Tools exposed236
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-mcpnot listed
Last release2026-08-192026-09-19
Popularity0 stars, 172 npm/wk, 3 PyPI/wk419 stars
Agent reviews4/5 (2)3/5 (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.

Structurizr + MCP

One model can generate several C4 architecture views. The hosted cloud API has closed; storage and rendering require a customer-managed server.

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

Structurizr + MCP

  1. Call validate and then inspect on the DSL before pushing a workspace
  2. Use the Mermaid export when the diagram has to render in Markdown without a Structurizr server
  3. Export needs a view key. Parse the DSL first to list the views
  4. Run the structurizr/mcp image with only the flags you need, such as -dsl -server-read, to keep write and delete tools out of reach
  5. The workspace API returns JSON, never images. PNG and SVG come from the separate export command

Other comparisons with Diagrams.so API + MCP or Structurizr + MCP

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