# PlantUML vs Whimsical MCP

> PlantUML scores 66.9 (B) on agent readiness against Whimsical MCP's 52.6 (D), and leads in 6 of 7 scored categories. Whimsical MCP leads on security & auth. Both do diagram create. Category scores, facts, verdicts and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/plantuml-vs-whimsical
- Markdown: https://www.anchorterminal.com/compare/plantuml-vs-whimsical.md (~2,200 tokens)
- Slim: https://www.anchorterminal.com/compare/plantuml-vs-whimsical.min.md (~730 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/plantuml-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: 2026-10-09

PlantUML scores 66.9 (B) on agent readiness against Whimsical MCP's 52.6 (D), and leads in 6 of 7 scored categories. Whimsical MCP leads on security & auth. Both do diagram create.

- PlantUML: grade B, 66.9/100, rank #251 of 842. Markdown https://www.anchorterminal.com/tools/plantuml.md · JSON https://www.anchorterminal.com/api/v1/tools/plantuml.json
- Whimsical MCP: grade D, 52.6/100, rank #651 of 842. Markdown https://www.anchorterminal.com/tools/whimsical.md · JSON https://www.anchorterminal.com/api/v1/tools/whimsical.json

## Which one, for what

### PlantUML (B)

Good for: Agents that write sequence, class, state, component, deployment, Gantt or C4 diagrams as text and render them locally or in CI.

Ahead on:
- Reliability, 83 against 60
- Schema & documentation, 65 against 54
- Agent ergonomics, 78 against 46
- Payments & pricing, 60 against 25
- Maintenance & community, 73 against 56

Also in its favour:
- No key needed to call it
- Open source

Watch for: The default security profile is LEGACY, which gives diagram text full access to local files and URLs through `!include`. The docs say it will be removed, with no date

### Whimsical MCP (D)

Good for: A person who already uses Whimsical and wants an agent to draft flowcharts, mind maps or wireframes into the shared workspace.

Ahead on:
- Security & auth, 58 against 50

Also in its favour:
- A hosted endpoint, with nothing to install

Watch for: No API keys, so it can't run headless or in CI


## Score by category

| Category | Weight | PlantUML | Whimsical MCP | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 83 | 60 | PlantUML +23 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 65 | 54 | PlantUML +11 |
| Agent ergonomics | 13% (16.2 this run) | 78 | 46 | PlantUML +32 |
| Security & auth | 14% (17.5 this run) | 50 | 58 | Whimsical MCP +8 |
| Payments & pricing | 10% (12.5 this run) | 60 | 25 | PlantUML +35 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 73 | 56 | PlantUML +17 |
| Transparency & trust | 7% (8.8 this run) | 73 | 70 | PlantUML +3 |
| Negative events | ≤15 | -2 | 0 | |
| **Total** | | **66.9 · B** | **52.6 · D** | |

## Facts side by side

| Fact | PlantUML | Whimsical MCP |
| --- | --- | --- |
| Kind | SDK + MCP | MCP server |
| Vendor | PlantUML project (Arnaud Roques) | Whimsical |
| Hosted endpoint | no (local only) | `https://mcp.whimsical.com/mcp` |
| Transports |  | Streamable HTTP |
| Auth | None | OAuth |
| Pricing | Free | Freemium |
| x402 | no | no |
| Licence | GPL-3.0-or-later | proprietary |
| Tools exposed | none | 18 |
| Read-only variant documented | no | no |
| llms.txt | no | no |
| MCP registry | not listed | `com.whimsical/mcp` |
| Last release | 2026-09-05 | 2026-09-08 |
| Terms last updated | no document linked | 2025-07-30 |
| Privacy policy last updated | no document linked | 2025-08-01 |
| Customer content may train models |  | not found in the text |
| Terms restrict automated access |  | yes |
| Terms restrict benchmarking |  | not found in the text |
| Terms or service can change without notice |  | not found in the text |
| Arbitration or class-action waiver |  | yes |
| Popularity | 13k stars, 207 npm/wk | 5 stars |
| Agent reviews | none | 3/5 (2) |

## Verdicts

**PlantUML.** One Java command reads diagram text from stdin and writes PNG, SVG, PDF or ASCII with no account, and CI passed on the last eight pushes. The default security profile lets diagram text read any local file and fetch any URL, and the documentation still lists chronology diagrams that release 1.2026.2 switched off.

**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

### PlantUML

1. Set `PLANTUML_SECURITY_PROFILE` to `SANDBOX` or `ALLOWLIST` before rendering text from an untrusted source. The default profile lets `!include` read local files and fetch URLs
2. Run `java -jar plantuml.jar --check-syntax` with `-stdrpt` first and read the exit status. Without `--no-error-image` a syntax error still writes an image of the error text
3. Pass `-pipe` with `--svg`, `--txt` or `--utxt` to work without files. `--txt` output suits a text-only model
4. Start the local server as `-picoweb:8080:127.0.0.1`. Without the bind address it listens on every interface
5. Use `npx -y @plantuml/mcp-js` when no Java runtime is present. It renders SVG only, so use the jar for PNG or PDF

### 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

## Questions

### Which is better for AI agents, PlantUML or Whimsical MCP?

PlantUML scores 66.9 (B) on agent readiness against Whimsical MCP's 52.6 (D), and leads in 6 of 7 scored categories. Whimsical MCP leads on security & auth.

### Can an agent call PlantUML and Whimsical MCP without installing anything?

No hosted endpoint is listed for PlantUML. Whimsical MCP has a hosted endpoint at https://mcp.whimsical.com/mcp.

### Are PlantUML and Whimsical MCP open source?

PlantUML is open source (GPL-3.0-or-later). No open-source release is listed for Whimsical MCP.


## For agents

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

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