A local MCP server previews Mermaid diagrams in Claude Code. Mermaid is a text format for describing diagrams, and MCP is a way for an agent to use an external tool.

It is for checking flowcharts and other diagrams written in Mermaid.

It gives the agent a local way to preview diagrams instead of relying on text alone.

mermaid — MCP server for Claude Code by veelenga

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Clone the repo

git clone --depth 1 https://github.com/veelenga/claude-mermaid

Made for: Claude Code.

Or install claude-mermaid, the plugin that ships this one along with the rest of its 1 skill, 1 MCP server.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/mcp/veelenga/claude-mermaid/mermaid/github.svg)](https://agentmods.dev/mcp/veelenga/claude-mermaid/mermaid)

Your own site

<a href="https://agentmods.dev/mcp/veelenga/claude-mermaid/mermaid"><img src="https://agentmods.dev/badge/mcp/veelenga/claude-mermaid/mermaid/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/mcp/veelenga/claude-mermaid/mermaid"><img src="https://agentmods.dev/badge/mcp/veelenga/claude-mermaid/mermaid.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session not measured What this adds to a session before it is invoked.

When invoked not measured Not applicable: nothing here is loaded into a session.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found in the catalogue.

Security

Grade A, and why

mermaid scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 11d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.mcp.json · 9 lines

What it actually says

{
  "mermaid": {
    "command": "npx",
    "args": [
      "-y",
      "claude-mermaid"
    ]
  }
}

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

11d ago First seen · 9 lines scan A c7ba550c3fdb

Subscribe to this mod's changes

mermaid is an MCP server published in the GitHub repository veelenga/claude-mermaid (205 stars, last pushed yesterday), licensed MIT. Its token cost is not measured: an MCP server costs its tool schemas, not its config file. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

Claude Code Design and UX mcp-server

mermaid

Getting it into your agent

Wrote this? Show the measurements

Grade A, and why

Nothing flagged

What it actually says

What this file has done since we first saw it

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