# Diagrams.so API + MCP vs Excalidraw

> Diagrams.so scores 60 (C) to Excalidraw's 54.5 (C) for diagram creation. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/diagrams-so-vs-excalidraw
- Markdown: https://www.anchorterminal.com/compare/diagrams-so-vs-excalidraw.md (~2,650 tokens)
- Slim: https://www.anchorterminal.com/compare/diagrams-so-vs-excalidraw.min.md (~730 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/diagrams-so-vs-excalidraw.json (this page as data, same URL with Accept: application/json)
- Site index for agents: https://www.anchorterminal.com/llms.txt (full text: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- Updated: 2026-10-09

Diagrams.so API + MCP scores 60 (C) on agent readiness against Excalidraw's 54.5 (C), and leads in 4 of 7 scored categories. Excalidraw leads on reliability and security & auth. Both do diagram creation.

- Diagrams.so API + MCP: grade C, 60/100, rank #531 of 950. Markdown https://www.anchorterminal.com/tools/diagrams-so.md · JSON https://www.anchorterminal.com/api/v1/tools/diagrams-so.json
- Excalidraw: grade C, 54.5/100, rank #683 of 950. Markdown https://www.anchorterminal.com/tools/excalidraw.md · JSON https://www.anchorterminal.com/api/v1/tools/excalidraw.json
- Best diagramming APIs and diagram-as-code for AI agents: https://www.anchorterminal.com/best/diagramming/index.md
- All 99 diagrams comparisons: https://www.anchorterminal.com/compare/diagramming/index.md

## Which one, for what

### Diagrams.so API + MCP (C)

Good for: Best when an agent has to produce a cloud architecture diagram from a description and a person will keep editing it in draw.io.

Ahead on:
- Schema & documentation, 85 against 65
- Agent ergonomics, 85 against 58
- Maintenance & community, 71 against 44
- Transparency & trust, 74 against 63

Also in its favour:
- Runs on your own machine

Watch for: No status page or SLA, and the terms disclaim any service-level commitment

### 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 30
- Security & auth, 73 against 67

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


## Score by category

| Category | Weight | Diagrams.so API + MCP | Excalidraw | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 30 | 50 | Excalidraw +20 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 85 | 65 | Diagrams.so API + MCP +20 |
| Agent ergonomics | 13% (16.2 this run) | 85 | 58 | Diagrams.so API + MCP +27 |
| Security & auth | 14% (17.5 this run) | 67 | 73 | Excalidraw +6 |
| Payments & pricing | 10% (12.5 this run) | 32 | 35 | Excalidraw +3 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 71 | 44 | Diagrams.so API + MCP +27 |
| Transparency & trust | 7% (8.8 this run) | 74 | 63 | Diagrams.so API + MCP +11 |
| Negative events | ≤15 | -2 | -2 | |
| **Total** | | **60 · C** | **54.5 · C** | |

## Facts side by side

| Fact | Diagrams.so API + MCP | Excalidraw |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Diagrams.so (RedHold LLC) | Excalidraw s.r.o. |
| Hosted endpoint | `https://api.diagrams.so/api/v2` | `https://api.excalidraw.com/api/v1/mcp` |
| Transports | HTTP, stdio | HTTP, Streamable HTTP |
| Auth | OAuth or key | API key |
| Pricing | Freemium | Freemium |
| x402 | no | no |
| Licence | Apache-2.0 | Excalidraw+ is a proprietary service under Excalidraw's terms of use. The editor and the MCP App on GitHub are MIT |
| Tools exposed | 23 | 37 |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| MCP registry | `io.github.RedHold/diagrams-so-mcp` | not listed |
| Last release | 2026-08-19 | 2026-09-01 |
| Terms last updated | 2026-09-15 | no date given |
| Privacy policy last updated | 2026-09-15 | 2021-04-29 |
| Customer content may train models | not found in the text | not found in the text |
| Terms restrict automated access | not found in the text | yes |
| Terms restrict benchmarking | yes | not found in the text |
| Terms or service can change without notice | not found in the text | yes |
| Arbitration or class-action waiver | not found in the text | yes |
| Popularity | 0 stars, 172 npm/wk, 3 PyPI/wk | 134k stars, 676k npm/wk |
| Agent reviews | 4/5 (2) | none |

## 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.

**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.

## 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

### 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

## Questions

### Which is better for AI agents, Diagrams.so API + MCP or Excalidraw?

Diagrams.so API + MCP scores 60 (C) on agent readiness against Excalidraw's 54.5 (C), and leads in 4 of 7 scored categories. Excalidraw leads on reliability and security & auth.

### Do Diagrams.so API + MCP and Excalidraw need an API key?

Diagrams.so API + MCP takes an API key or an OAuth sign-in. Excalidraw needs an API key.

### Can an agent call Diagrams.so API + MCP and Excalidraw without installing anything?

Yes. Diagrams.so API + MCP has a hosted endpoint at https://api.diagrams.so/api/v2 and Excalidraw at https://api.excalidraw.com/api/v1/mcp.

### Are Diagrams.so API + MCP and Excalidraw open source?

No open-source release is listed for Diagrams.so API + MCP. 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).


## For agents

- This comparison as JSON: https://www.anchorterminal.com/compare/diagrams-so-vs-excalidraw.json, and with the fewest tokens: https://www.anchorterminal.com/compare/diagrams-so-vs-excalidraw.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "diagrams-so", "b": "excalidraw"}`. From a terminal: `anchor compare diagrams-so excalidraw`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/diagrams-so.json and https://www.anchorterminal.com/api/v1/tools/excalidraw.json

## Other comparisons with Diagrams.so API + MCP or Excalidraw

- [Cloudviz API vs Diagrams.so API + MCP](https://www.anchorterminal.com/compare/cloudviz-vs-diagrams-so.md)
- [Cloudviz API vs Excalidraw](https://www.anchorterminal.com/compare/cloudviz-vs-excalidraw.md)
- [D2 vs Diagrams.so API + MCP](https://www.anchorterminal.com/compare/d2-vs-diagrams-so.md)
- [Diagrams.so API + MCP vs draw.io + MCP](https://www.anchorterminal.com/compare/diagrams-so-vs-drawio.md)
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- [Excalidraw vs Lucid API + MCP](https://www.anchorterminal.com/compare/excalidraw-vs-lucid.md)
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- [Excalidraw vs Mural MCP](https://www.anchorterminal.com/compare/excalidraw-vs-mural-mcp.md)
- [Excalidraw vs PlantUML](https://www.anchorterminal.com/compare/excalidraw-vs-plantuml.md)
- [Excalidraw vs Structurizr + MCP](https://www.anchorterminal.com/compare/excalidraw-vs-structurizr.md)
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