# Kroki vs Mermaid Chart MCP

> Kroki scores 59.2 (C) to Mermaid Chart MCP's 31.4 (F) for diagrams as code. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/kroki-vs-mermaid-chart
- Markdown: https://www.anchorterminal.com/compare/kroki-vs-mermaid-chart.md (~2,450 tokens)
- Slim: https://www.anchorterminal.com/compare/kroki-vs-mermaid-chart.min.md (~730 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/kroki-vs-mermaid-chart.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

Kroki scores 59.2 (C) on agent readiness against Mermaid Chart MCP's 31.4 (F), and leads in every scored category. Both do diagrams as code.

- Kroki: grade C, 59.2/100, rank #558 of 950. Markdown https://www.anchorterminal.com/tools/kroki.md · JSON https://www.anchorterminal.com/api/v1/tools/kroki.json
- Mermaid Chart MCP: grade F, 31.4/100, rank #939 of 950. Markdown https://www.anchorterminal.com/tools/mermaid-chart.md · JSON https://www.anchorterminal.com/api/v1/tools/mermaid-chart.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

### Kroki (C)

Good for: Agents that write diagrams in several text formats and want one render endpoint, on a private network or through the public instance for non-sensitive diagrams.

Ahead on:
- Reliability, 74 against 15
- Schema & documentation, 48 against 32
- Agent ergonomics, 70 against 34
- Security & auth, 56 against 20
- Payments & pricing, 60 against 45
- Maintenance & community, 86 against 53
- Transparency & trust, 62 against 45

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

Watch for: GHSA-wmpp-fj9c-w766 (CVSS 9.8) allowed unauthenticated remote code execution on `/tikz/svg` in versions 0.21.0 up to 0.32.0, whatever the safe mode. Fixed 3 August 2026

### Mermaid Chart MCP (F)

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

Also in its favour:
- A hosted endpoint, with nothing to install
- No incidents deducted, where Kroki loses 5 points for them

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


## Score by category

| Category | Weight | Kroki | Mermaid Chart MCP | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 74 | 15 | Kroki +59 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 48 | 32 | Kroki +16 |
| Agent ergonomics | 13% (16.2 this run) | 70 | 34 | Kroki +36 |
| Security & auth | 14% (17.5 this run) | 56 | 20 | Kroki +36 |
| Payments & pricing | 10% (12.5 this run) | 60 | 45 | Kroki +15 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 86 | 53 | Kroki +33 |
| Transparency & trust | 7% (8.8 this run) | 62 | 45 | Kroki +17 |
| Negative events | ≤15 | -5 | 0 | |
| **Total** | | **59.2 · C** | **31.4 · F** | |

## Facts side by side

| Fact | Kroki | Mermaid Chart MCP |
| --- | --- | --- |
| Kind | HTTP API | MCP server |
| Vendor | Yuzu tech | Mermaid Chart |
| Hosted endpoint | no (local only) | `https://mcp.mermaid.ai/mcp` |
| Transports | HTTP | Streamable HTTP, SSE (legacy) |
| Auth | None | OAuth or key |
| Pricing | Free | Freemium |
| x402 | no | no |
| Licence | MIT | none |
| Tools exposed | none | 25 |
| Read-only variant documented | no | no |
| llms.txt | no | no |
| MCP registry | not listed | `com.mermaidchart/mermaid-mcp` |
| Last release | 2026-10-05 | 2026-09-17 |
| Terms last updated | no document linked | no date given |
| Privacy policy last updated | no document linked | 2024-09-13 |
| Customer content may train models |  | not found in the text |
| Terms restrict automated access |  | not found in the text |
| Terms restrict benchmarking |  | yes |
| Terms or service can change without notice |  | not found in the text |
| Arbitration or class-action waiver |  | not found in the text |
| Popularity | 4.4k stars | 395 npm/wk |
| Agent reviews | none | 2.5/5 (2) |

## Verdicts

**Kroki.** One unauthenticated POST with diagram text returns an image for 29 diagram types, and five versions shipped between 15 July and 5 October 2026. Four advisories were published in July and August 2026, one an unauthenticated remote code execution on `/tikz/svg`, all fixed. No OpenAPI file exists, and the public instance has no terms, privacy policy or status page.

**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

### Kroki

1. Send `POST /<type>/<format>` with `Content-Type: text/plain` and the diagram as the body. This avoids the deflate and base64 encoding that GET needs
2. Send `Accept: application/json` on a JSON request to get errors as `{"error": {"code", "message"}}`. With an SVG Accept header the error arrives as an image
3. Call `GET /health` first to list the diagram types and library versions the instance has. Mermaid, BPMN, Excalidraw and diagrams.net need companion containers
4. Run 0.32.1 or later before rendering untrusted text. Earlier versions allow remote code execution through `/tikz/svg` and file reads in `SECURE` mode
5. Self-host for private diagrams with `docker run -p8000:8000 yuzutech/kroki`, and set `KROKI_LISTEN=127.0.0.1:8000` or a network rule, since the server has no authentication

### 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, Kroki or Mermaid Chart MCP?

Kroki scores 59.2 (C) on agent readiness against Mermaid Chart MCP's 31.4 (F), and leads in every scored category.

### Do Kroki and Mermaid Chart MCP need an API key?

Kroki needs no key. Mermaid Chart MCP takes an API key or an OAuth sign-in.

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

No hosted endpoint is listed for Kroki. Mermaid Chart MCP has a hosted endpoint at https://mcp.mermaid.ai/mcp.

### Are Kroki and Mermaid Chart MCP open source?

Kroki is open source (MIT). No open-source release is listed for Mermaid Chart MCP.


## For agents

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

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