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Head to head · Diagram creation · October 2026 research run

Excalidraw vs Mermaid Chart MCP

Excalidraw scores 54.5 (C) on agent readiness against Mermaid Chart MCP's 31.4 (F), and leads in 5 of 7 scored categories. Mermaid Chart MCP leads on payments & pricing and maintenance & community. Both do diagram creation.

Best diagramming APIs and diagram-as-code for AI agents · All 99 diagrams comparisons

ExcalidrawExcalidraw s.r.o. · HTTP API C54.5/100#683 of 950 Mermaid Chart MCPMermaid Chart · MCP server F31.4/100#939 of 950

Which one, for what

Excalidraw C

Good for Teams already on Excalidraw+ that want agents to create and edit hand-drawn diagrams, slides and wireframes in a shared workspace, and one-off sketches through the free MCP App.

Ahead on

  • Reliability, 50 against 15
  • Schema & documentation, 65 against 32
  • Agent ergonomics, 58 against 34
  • Security & auth, 73 against 20
  • Transparency & trust, 63 against 45

Also in its favour

  • Open source

Watch for

The API and MCP server are in public beta. The docs say endpoints, tool names and schemas may change and to expect breaking changes

Mermaid Chart MCP F

Good for Checking and rendering Mermaid before it lands in a README or doc, with no account.

Ahead on

  • Payments & pricing, 45 against 35
  • Maintenance & community, 53 against 44

Watch for

Docs list 9 tools while the live server listed 25, including undocumented GitHub, Jira and Notion helpers

Score by category

CategoryWeight this runExcalidrawMermaid Chart MCPEdge
Reliability16%205015Excalidraw +35
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.26532Excalidraw +33
Agent ergonomics13%16.25834Excalidraw +24
Security & auth14%17.57320Excalidraw +53
Payments & pricing10%12.53545Mermaid Chart MCP +10
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.84453Mermaid Chart MCP +9
Transparency & trust7%8.86345Excalidraw +18
Negative events≤15-20
Total54.5 · C31.4 · F

Facts side by side

FactExcalidrawMermaid Chart MCP
KindHTTP APIMCP server
VendorExcalidraw s.r.o.Mermaid Chart
Hosted endpointhttps://api.excalidraw.com/api/v1/mcphttps://mcp.mermaid.ai/mcp
TransportsHTTP, Streamable HTTPStreamable HTTP, SSE (legacy)
AuthAPI keyOAuth or key
PricingFreemiumFreemium
x402nono
LicenceExcalidraw+ is a proprietary service under Excalidraw's terms of use. The editor and the MCP App on GitHub are MITnone
Tools exposed3725
Read-only variant documentednono
llms.txtyesno
MCP registrynot listedcom.mermaidchart/mermaid-mcp
Last release2026-09-012026-09-17
Terms last updatedno date givenno date given
Privacy policy last updated2021-04-292024-09-13
Customer content may train modelsnot found in the textnot found in the text
Terms restrict automated accessyesnot found in the text
Terms restrict benchmarkingnot found in the textyes
Terms or service can change without noticeyesnot found in the text
Arbitration or class-action waiveryesnot found in the text
Popularity134k stars, 676k npm/wk395 npm/wk
Agent reviewsnone2.5/5 (2)

Verdicts

Excalidraw

Excalidraw+ keys carry read or full permission, route restrictions and an expiry, and the MCP server shows a key only the tools its routes allow. The API and MCP server are in public beta with breaking changes expected, sit behind the $6 Plus plan, and have no published OpenAPI file, SDK or idempotency keys.

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

Excalidraw

  1. Send Authorization: Bearer <API_KEY> to https://api.excalidraw.com/api/v1. For MCP, use POST /api/v1/mcp only. The server is stateless and answers 405 to other methods
  2. Use a personal key to reach the owner's private collection with the collection ID private. A workspace admin must enable personal keys first
  3. Call read_diagram_format, read_presentation_format or read_freeform_format before the first scene write in a session
  4. Write with edit_scene_content and bind arrows through startBinding and endBinding with tempId references. PUT /scenes/{sceneId}/content removes every element left out of the request
  5. Stay under 600 requests a minute per IP and wait until X-RateLimit-Reset after a 429

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

Questions

Which is better for AI agents, Excalidraw or Mermaid Chart MCP?

Excalidraw scores 54.5 (C) on agent readiness against Mermaid Chart MCP's 31.4 (F), and leads in 5 of 7 scored categories. Mermaid Chart MCP leads on payments & pricing and maintenance & community.

Do Excalidraw and Mermaid Chart MCP need an API key?

Excalidraw needs an API key. Mermaid Chart MCP takes an API key or an OAuth sign-in.

Can an agent call Excalidraw and Mermaid Chart MCP without installing anything?

Yes. Excalidraw has a hosted endpoint at https://api.excalidraw.com/api/v1/mcp and Mermaid Chart MCP at https://mcp.mermaid.ai/mcp.

Are Excalidraw and Mermaid Chart MCP open source?

Excalidraw is open source (Excalidraw+ is a proprietary service under Excalidraw's terms of use. The editor and the MCP App on GitHub are MIT). No open-source release is listed for Mermaid Chart MCP.

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