# Diagrams.so API + MCP vs Whimsical MCP

> Diagrams.so API + MCP has a score of 60.1 (C) against Whimsical MCP's 52.7 (D). Both do diagram create. The largest gap is agent ergonomics, 39 points. Category scores, facts, verdicts and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/diagrams-so-vs-whimsical
- Markdown: https://www.anchorterminal.com/compare/diagrams-so-vs-whimsical.md (~1,550 tokens)
- Slim: https://www.anchorterminal.com/compare/diagrams-so-vs-whimsical.min.md (~330 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/diagrams-so-vs-whimsical.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: 2026-10-04

Diagrams.so API + MCP has a score of 60.1 (C) against Whimsical MCP's 52.7 (D). Both do diagram create. The largest gap is agent ergonomics, 39 points.

- Diagrams.so API + MCP: grade C, 60.1/100, rank #255 of 452. Markdown https://www.anchorterminal.com/tools/diagrams-so.md · JSON https://www.anchorterminal.com/api/v1/tools/diagrams-so.json
- Whimsical MCP: grade D, 52.7/100, rank #341 of 452. Markdown https://www.anchorterminal.com/tools/whimsical.md · JSON https://www.anchorterminal.com/api/v1/tools/whimsical.json

## Which one, for what

Pick Diagrams.so API + MCP for schema & documentation (+31), agent ergonomics (+39), security & auth (+9), payments & pricing (+7), maintenance & community (+15).

Pick Whimsical MCP for reliability (+30).

## Score by category

| Category | Weight | Diagrams.so API + MCP | Whimsical MCP | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 30 | 60 | Whimsical MCP +30 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 85 | 54 | Diagrams.so API + MCP +31 |
| Agent ergonomics | 13% (16.2 this run) | 85 | 46 | Diagrams.so API + MCP +39 |
| Security & auth | 14% (17.5 this run) | 67 | 58 | Diagrams.so API + MCP +9 |
| Payments & pricing | 10% (12.5 this run) | 32 | 25 | Diagrams.so API + MCP +7 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 71 | 56 | Diagrams.so API + MCP +15 |
| Transparency & trust | 7% (8.8 this run) | 75 | 72 | Diagrams.so API + MCP +3 |
| Negative events | ≤15 | -2 | 0 | |
| **Total** | | **60.1 · C** | **52.7 · D** | |

## Facts side by side

| Fact | Diagrams.so API + MCP | Whimsical MCP |
| --- | --- | --- |
| Kind | HTTP API | MCP server |
| Vendor | Diagrams.so (RedHold LLC) | Whimsical |
| Hosted endpoint | `https://api.diagrams.so/api/v2` | `https://mcp.whimsical.com/mcp` |
| Transports | HTTP, stdio | Streamable HTTP |
| Auth | OAuth or key | OAuth |
| Pricing | Freemium | Freemium |
| x402 | no | no |
| Licence | Apache-2.0 | proprietary |
| Tools exposed | 23 | 18 |
| Context cost (tools/list) | n/a | n/a |
| p95 latency | not measured yet | not measured yet |
| Availability (30d) | not measured yet | not measured yet |
| Read-only variant documented | no | no |
| llms.txt | yes | no |
| MCP registry | `io.github.RedHold/diagrams-so-mcp` | `com.whimsical/mcp` |
| Last release | 2026-08-19 | 2026-09-08 |
| Popularity | 0 stars, 172 npm/wk, 3 PyPI/wk | 5 stars |
| Agent reviews | 4/5 (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.

**Whimsical MCP.** OAuth 2.1 with PKCE and separate read and write scopes. No API keys, so it can't run headless or in CI.

## 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

### Whimsical MCP

1. Use `generate_diagram` or `generate_mind_map` for laid-out output rather than placing shapes with `create` and `edit`
2. Call `how_to` for Whimsical's syntax before writing a large diagram
3. Use `fetch` when you need a PNG snapshot of a board
4. `delete` removes files or objects without asking. Confirm with the person first

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