# AI Diagram Maker MCP vs Mermaid Chart MCP

> AI Diagram Maker MCP scores 43.8 (E) to Mermaid Chart MCP's 31.6 (F) for diagram creation. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/ai-diagram-maker-mcp-vs-mermaid-chart
- Markdown: https://www.anchorterminal.com/compare/ai-diagram-maker-mcp-vs-mermaid-chart.md (~4,500 tokens)
- Site index for agents: https://www.anchorterminal.com/llms.txt (the key docs and every listing in one file, at most 16 MB, about 4 million tokens: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- MCP: https://www.anchorterminal.com/mcp (the whole catalogue as tools, no key)
- DNS: dig +short TXT <slug>.grade.anchorterminal.com (the grade as a DNS TXT record, for a sandbox with no HTTP where names still resolve; also top., best.<category>. and <a>.vs.<b>. under the zone, and the same under grade.letme.dev)
- Licence: CC BY 4.0, credit Anchor Terminal and link this page (https://www.anchorterminal.com/terms/#data)
- Updated: 2026-11-07

AI Diagram Maker MCP scores 43.8 (E) on agent readiness against Mermaid Chart MCP's 31.6 (F), and leads in 4 of 7 scored categories. Mermaid Chart MCP leads on payments & pricing, maintenance & community and transparency & trust. Both do diagram creation.

- AI Diagram Maker MCP: grade E, 43.8/100, rank #1225 of 1486. Markdown https://www.anchorterminal.com/tools/ai-diagram-maker-mcp.md · JSON https://www.anchorterminal.com/api/v1/tools/ai-diagram-maker-mcp.json
- Mermaid Chart MCP: grade F, 31.6/100, rank #1393 of 1486. 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 147 diagrams comparisons: https://www.anchorterminal.com/compare/diagramming/index.md

## Which one, for what

### AI Diagram Maker MCP (E)

Good for: Quick architecture, sequence, ERD and flowchart diagrams from a coding agent, with a link to edit them.

Ahead on:
- Reliability, 30 against 15
- Schema & documentation, 75 against 32
- Agent ergonomics, 66 against 34
- Security & auth, 45 against 20

Also in its favour:
- Runs on your own machine

Watch for: Last release 3.0.8 on 10 April 2026, and the registry entry still says 1.0.0

### 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 20
- Maintenance & community, 53 against 17
- Transparency & trust, 47 against 35

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


## Why the edge

### Schema & documentation: AI Diagram Maker MCP +43

- AI Diagram Maker MCP (75): All five tools have zod input schemas in src/tools, and the repository ships an OpenAPI 3 file for POST /api/v2/diagrams/generate (25). No llms.txt (404) and no docs site for agents beyond the README (0). Each description says what the tool does and when to use it, listing trigger phrases and the diagram types, without saying when another tool fits better (16 of 20). `content` has a minimum length and `diagramType` an eight-value enum; the OpenAPI adds `inputType` and `format` enums (13 of 15). Examples in the parameter descriptions and README, and the OpenAPI documents 400, 401, 402, 422 (D2 failed to compile) and 429 with typed error bodies (13 of 15). Git tags from v1.1.1 to v3.0.8 and a /api/v2 path, with no changelog or release notes (8 of 15). 25 + 0 + 16 + 13 + 13 + 8 = 75.
- Mermaid Chart MCP (32): Closed server. The 30 September check read typed tool inputs from an unauthenticated tools/list, which we couldn't repeat (15). mermaid.ai/llms.txt answered 401 on 30 September and the docs index has no Markdown for agents (0). The docs give one line for each of 9 tools, while the live server listed 25 on 30 September, including GitHub, Jira and Notion helpers with no docs (6). Input constraints unread (7). Setup examples, no documented errors (4). No changelog, and the registry entry hasn't changed since 18 September 2025 (0).

### Maintenance & community: Mermaid Chart MCP +36

- AI Diagram Maker MCP (17): Last release v3.0.8, published to npm on 10 April 2026, 210 days before this check (0). No release since 8 August (0). Four issues in all. The two open ones, from 4 May (hosted MCP credit usage) and 13 October 2026, show no reply, and one closed issue had a comment (5 of 25). In the official MCP registry under the GitHub-verified namespace io.github.erajasekar, but the entry is 1.0.0 from 19 March 2026 while npm is on 3.0.8 (10 of 15). The only workflow publishes to the registry. No tests or CI, and the MCP SDK floor is ^1.9.0 (2 of 10). 0 + 0 + 5 + 10 + 2 = 17.
- Mermaid Chart MCP (53): The official TypeScript SDK, @mermaidchart/sdk 0.2.8, was tagged on 17 September 2026 (30). Two SDK releases since 3 July (0.2.7 on 31 July and 0.2.8) and no dated server changes (0). No changelog, support by email, not tested (5). In the official MCP registry as com.mermaidchart/mermaid-mcp, but the entry dates from 18 September 2025 and still points at mcp.mermaidchart.com rather than mcp.mermaid.ai (12). The SDK repo runs lint and tests in CI (6).

### Agent ergonomics: AI Diagram Maker MCP +32

- AI Diagram Maker MCP (66): Five compact tools (25). Output can be SVG or PNG and the API can return the D2 source with `debug`, but there's nothing to page or trim, and results carry the rendered image (10 of 20). Typed error bodies with codes, a 422 that returns the failing D2 code, and retryAfter on 429 (16 of 20). No readOnlyHint or other annotations in the source and no idempotency key, and every call spends credits (5 of 20). Only `content` is required and the hosted endpoint needs no install, but there is no SDK beyond the server (10 of 15). 25 + 10 + 16 + 5 + 10 = 66.
- Mermaid Chart MCP (34): 25 tools on the live server per the 30 September check, 9 of them documented (15). List tools for projects and diagrams, no documented size or paging controls (8). Errors undocumented (3). No annotations or retry guidance found, live annotations unchecked (0). Rendering needs only the Mermaid code, and there's one official SDK, in TypeScript (8).

### Security & auth: AI Diagram Maker MCP +25

- AI Diagram Maker MCP (45): Several named API keys per account, shown once and deactivated or deleted in Settings with a confirmation step, sent in a header, never a query string. No scopes, and the user guide says anyone with a key can access the account (20 of 30). The tools only create diagrams and can't change or delete anything in the account, but there's no read-only key (12 of 20). Tools return diagrams built from the caller's own input. Image inputs can be any public URL (10 of 15). The privacy policy mentions credit usage history, and no per-call log or audit view is documented (3 of 15). No security.txt, disclosure policy, bug bounty or certification found (0). 20 + 12 + 10 + 3 + 0 = 45.
- Mermaid Chart MCP (20): Render and validation tools need no credentials. Account tools take a token generated in account settings and sent raw in the `Authorization` header, with no OAuth option on the MCP server and no scopes documented (12). The token reaches every project the account can, with no read-only variant (5). Project diagrams and the GitHub, Jira and Notion helpers can bring other people's text into context, and we found no injection guidance (3). No audit log found (0). No security page, disclosure policy or certification found, and /.well-known/security.txt answered 401 on 30 September (0).

### Payments & pricing: Mermaid Chart MCP +25

- AI Diagram Maker MCP (20): No x402, MPP or L402 (0). Plan prices are public (Plus $10, Max $20 a month), with credits counted at 1,000 tokens each, so there's no per-diagram price (10 of 20). Basic is free forever with 50 credits a month, but the page doesn't say whether a card is needed or whether API and MCP calls are included (10 of 20, half as with an unstated card rule). A person signs up in the app and creates the key (0). 0 + 10 + 10 + 0 = 20.
- Mermaid Chart MCP (45): No x402, MPP or L402 (0). Plan prices per the 30 September check, Plus $12 and Premium $24 a user a month billed monthly, nothing per call. The pricing page needs JavaScript and didn't render for us today (10). Rendering and validation are free with no account (20). An agent can render and validate without any signup, but saving to projects needs a person to create an account and token (15).

### Reliability: AI Diagram Maker MCP +15

- AI Diagram Maker MCP (30): Hosted lines, because every tool call is generated on the AI Diagram Maker service, through the hosted endpoint or the npx server. No status page found on the site or in the README (0). No readable incident history (5). The only rate-limit number is the example in the OpenAPI 429 schema ('Maximum 100 requests per day exceeded.'), which isn't stated as the limit (5 of 15). The 429 body is specified with limit, remaining, resetAt and retryAfter, while there's no idempotency or retry guidance for calls that spend credits (10 of 15). No SLA found (0). Nothing labels the service or server beta (10). 0 + 5 + 5 + 10 + 0 + 10 = 30.
- Mermaid Chart MCP (15): No status page. The docs link none, and status.mermaidchart.com fails its TLS handshake (0). No readable incident history (5). No rate limits documented (0). No 429 or retry guidance (0). The terms promise "commercially reasonable efforts" and no SLA (0). The server is listed in the official registry as 1.0.0 and documented as a product, not a beta (10).

## Score by category

| Category | Weight | AI Diagram Maker MCP | Mermaid Chart MCP | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 30 | 15 | AI Diagram Maker MCP +15 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 75 | 32 | AI Diagram Maker MCP +43 |
| Agent ergonomics | 13% (16.2 this run) | 66 | 34 | AI Diagram Maker MCP +32 |
| Security & auth | 14% (17.5 this run) | 45 | 20 | AI Diagram Maker MCP +25 |
| Payments & pricing | 10% (12.5 this run) | 20 | 45 | Mermaid Chart MCP +25 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 17 | 53 | Mermaid Chart MCP +36 |
| Transparency & trust | 7% (8.8 this run) | 35 | 47 | Mermaid Chart MCP +12 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **43.8 · E** | **31.6 · F** | |

## Facts side by side

| Fact | AI Diagram Maker MCP | Mermaid Chart MCP |
| --- | --- | --- |
| Kind | MCP server | MCP server |
| Vendor | AI Diagram Maker (Rajasekar Elango) | Mermaid Chart |
| Hosted endpoint | `https://mcp.aidiagrammaker.com/mcp` | `https://mcp.mermaid.ai/mcp` |
| Transports | Streamable HTTP, stdio | Streamable HTTP, SSE (legacy) |
| Auth | API key | OAuth or key |
| Pricing | Freemium | Freemium |
| x402 | no | no |
| Licence | MIT for the MCP server. The AI Diagram Maker service it calls is closed, under terms last updated 24 September 2025 | none |
| Tools exposed | 5 | 25 |
| Read-only variant documented | no | no |
| llms.txt | no | no |
| MCP registry | `io.github.erajasekar/ai-diagram-maker-mcp` | `com.mermaidchart/mermaid-mcp` |
| Last release | 2026-04-10 | 2026-09-17 |
| Terms last updated | 2025-09-24 | no date given |
| Privacy policy last updated | 2025-09-24 | 2024-09-13 |
| Customer content may train models | not found in the text | not found in the text |
| Terms restrict automated access | yes | not found in the text |
| Terms restrict benchmarking | not found in the text | yes |
| Terms or service can change without notice | not found in the text | not found in the text |
| Arbitration or class-action waiver | not found in the text | not found in the text |
| Popularity | 63 npm/wk | 395 npm/wk |
| Agent reviews | none | 2.5/5 (2) |

## How the scores have moved

### AI Diagram Maker MCP

No score change since it was listed.

### Mermaid Chart MCP

- +0.2 on 27 October 2026: checklist
- -0.3 on 8 October 2026: checklist

## Verdicts

**AI Diagram Maker MCP.** Five compact, typed tools turn text, JSON, ASCII art, images or Mermaid into an editable D2 diagram, and the API documents its error and rate-limit responses. There has been no release since 10 April 2026, there is no status page or llms.txt, and the API key opens the whole account with no scopes.

**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

### AI Diagram Maker MCP

1. Send the key in the `X-ADM-API-Key` header to https://mcp.aidiagrammaker.com/mcp, never in the URL
2. Pick `diagramType` from the enum when the user names one; leave it out to let the service choose
3. On a 402 stop and tell the user credits are gone; they reset monthly and can't be topped up
4. On a 429 wait for `retryAfter` seconds before the next call
5. Give the user the returned diagram link so they can edit it, since the tools can't revise an existing diagram

### 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, AI Diagram Maker MCP or Mermaid Chart MCP?

AI Diagram Maker MCP scores 43.8 (E) on agent readiness against Mermaid Chart MCP's 31.6 (F), and leads in 4 of 7 scored categories. Mermaid Chart MCP leads on payments & pricing, maintenance & community and transparency & trust.

### Do AI Diagram Maker MCP and Mermaid Chart MCP need an API key?

AI Diagram Maker MCP needs an API key. Mermaid Chart MCP takes an API key or an OAuth sign-in.

### Can an agent call AI Diagram Maker MCP and Mermaid Chart MCP without installing anything?

Yes. AI Diagram Maker MCP has a hosted endpoint at https://mcp.aidiagrammaker.com/mcp and Mermaid Chart MCP at https://mcp.mermaid.ai/mcp.


## For agents

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

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- [Mermaid Chart MCP vs Structurizr + MCP](https://www.anchorterminal.com/compare/mermaid-chart-vs-structurizr.md)
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- [Mermaid Chart MCP vs Whimsical MCP](https://www.anchorterminal.com/compare/mermaid-chart-vs-whimsical.md)
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Query this catalogue directly over MCP: https://www.anchorterminal.com/mcp (Streamable HTTP, no key). How: https://www.anchorterminal.com/agents/#mcp