mermaid-skill MCP — Use Cases, Install & Live Demo

Why use it

Key features

Covers 10+ Mermaid diagram types
Local render via mmdc (PNG / SVG / PDF)
Automatic layout hints to avoid crossing edges
Iterates on diagrams based on feedback
Works inside your repo, diagrams committed alongside code

Live Demo

What it looks like in practice

mermaid-skill.replay ▶ ready

0/0

Install

Pick your client

~/Library/Application Support/Claude/claude_desktop_config.json · Windows: %APPDATA%\Claude\claude_desktop_config.json

{
  "mcpServers": {
    "mermaid-skill": {
      "command": "git",
      "args": [
        "clone",
        "https://github.com/Agents365-ai/mermaid-skill",
        "~/.claude/skills/mermaid-skill"
      ],
      "_inferred": true
    }
  }
}

Open Claude Desktop → Settings → Developer → Edit Config. Restart after saving.

~/.cursor/mcp.json · .cursor/mcp.json

{
  "mcpServers": {
    "mermaid-skill": {
      "command": "git",
      "args": [
        "clone",
        "https://github.com/Agents365-ai/mermaid-skill",
        "~/.claude/skills/mermaid-skill"
      ],
      "_inferred": true
    }
  }
}

Cursor uses the same mcpServers schema as Claude Desktop. Project config wins over global.

VS Code → Cline → MCP Servers → Edit

{
  "mcpServers": {
    "mermaid-skill": {
      "command": "git",
      "args": [
        "clone",
        "https://github.com/Agents365-ai/mermaid-skill",
        "~/.claude/skills/mermaid-skill"
      ],
      "_inferred": true
    }
  }
}

Click the MCP Servers icon in the Cline sidebar, then "Edit Configuration".

~/.codeium/windsurf/mcp_config.json

{
  "mcpServers": {
    "mermaid-skill": {
      "command": "git",
      "args": [
        "clone",
        "https://github.com/Agents365-ai/mermaid-skill",
        "~/.claude/skills/mermaid-skill"
      ],
      "_inferred": true
    }
  }
}

Same shape as Claude Desktop. Restart Windsurf to pick up changes.

~/.continue/config.json

{
  "mcpServers": [
    {
      "name": "mermaid-skill",
      "command": "git",
      "args": [
        "clone",
        "https://github.com/Agents365-ai/mermaid-skill",
        "~/.claude/skills/mermaid-skill"
      ]
    }
  ]
}

Continue uses an array of server objects rather than a map.

~/.config/zed/settings.json

{
  "context_servers": {
    "mermaid-skill": {
      "command": {
        "path": "git",
        "args": [
          "clone",
          "https://github.com/Agents365-ai/mermaid-skill",
          "~/.claude/skills/mermaid-skill"
        ]
      }
    }
  }
}

Add to context_servers. Zed hot-reloads on save.

claude mcp add mermaid-skill -- git clone https://github.com/Agents365-ai/mermaid-skill ~/.claude/skills/mermaid-skill

One-liner. Verify with claude mcp list. Remove with claude mcp remove.

Use Cases

Real-world ways to use mermaid-skill

Draw an architecture diagram for your current project

👤 Devs writing docs, ADRs, or onboarding guides ⏱ ~20 min beginner

When to use: You keep explaining your architecture in Slack and want a picture.

Prerequisites

mmdc installed — npm i -g @mermaid-js/mermaid-cli
Skill installed — git clone https://github.com/Agents365-ai/mermaid-skill ~/.claude/skills/mermaid-skill

Flow

Describe the system

Use mermaid-skill. Draw a flowchart of our service: client → API gateway → (auth / orders / payments) → Postgres / Redis / Stripe.✓ Copied

→ .mmd source with meaningful node names, rendered to PNG in docs/
Add details

Add labels on each edge showing the protocol (HTTPS, gRPC, TCP) and auth type.✓ Copied

→ Updated source and re-render
Commit it

Commit docs/architecture.mmd and its PNG.✓ Copied

→ git add and commit run

Outcome: A living diagram in the repo, not a stale slide in Confluence.

Pitfalls

Diagram becomes a maze of edges — Let Claude use subgraphs and direction hints; don't cram everything on one layer

Combine with: filesystem · git

Produce a sequence diagram while debugging

👤 Engineers tracing a cross-service bug ⏱ ~15 min beginner

When to use: You're trying to understand an async interaction and English isn't cutting it.

Flow

Describe the flow

Use mermaid-skill. Sequence diagram: browser → SSR → auth service → session store → page render, with failure mode when session is stale.✓ Copied

→ Sequence diagram with the failure annotated
Annotate the bug

Highlight the line where the bug manifests.✓ Copied

→ Annotated box/note on the offending message

Outcome: A picture you can paste in the bug ticket.

Generate an ERD from your actual database schema

👤 Data engineers, backend devs ⏱ ~20 min intermediate

When to use: You want a visual of your schema for a design review.

Flow

Introspect

Use mermaid-skill. Read the schema.sql (or query the live DB via postgres MCP) and produce a Mermaid ERD.✓ Copied

→ .mmd ERD with relationships and cardinalities
Trim noise

Drop audit tables and focus on the core domain entities.✓ Copied

→ Trimmed ERD

Outcome: An accurate ERD without manual drawing.

Pitfalls

Cardinalities wrong when inferred — Provide the actual foreign-key definitions; don't let the model guess

Combine with: postgres

Combinations

Pair with other MCPs for X10 leverage

mermaid-skill + filesystem

Keep diagrams alongside the code they describe

For every service in services/, add a docs/architecture.mmd and render it.✓ Copied

mermaid-skill + postgres

Auto-generate ERDs from live databases

Connect to the staging DB and render its schema as a Mermaid ERD.✓ Copied

mermaid-skill + git

Diagram stays versioned with code changes

Commit updated diagrams in the same PR as the code changes they describe.✓ Copied

Tools

What this MCP exposes

Tool	Inputs	When to call	Cost
write_mermaid	description, diagram type	Any diagram request	0
render_mmdc	.mmd path, output format	After source is final	local mmdc
iterate_diagram	current diagram + feedback	Reviewer feedback	0

Cost & Limits

What this costs to run

API quota: None
Tokens per call: Small — Mermaid source is compact
Monetary: Free (mmdc is open source)
Tip: For big diagrams, generate subgraphs separately to avoid retrying large rewrites.

Security

Permissions, secrets, blast radius

Credential storage: None

Data egress: None from skill itself

Troubleshooting

Common errors and fixes

mmdc not found

Install globally: npm i -g @mermaid-js/mermaid-cli

Verify: which mmdc

Render fails with syntax error

Mermaid has version-specific syntax; run mmdc --version and match the skill's assumed version

Verify: mmdc --version

Diagram is a mess of crossing edges

Add direction hints (TD/LR), group with subgraphs, or split into multiple diagrams

Alternatives

mermaid-skill vs others

Alternative	When to use it instead	Tradeoff
PlantUML / draw.io	You need more control or non-Mermaid syntax	More setup, different rendering toolchain
paperbanana-skill	Academic publication-quality diagrams	Heavier; different aesthetic goals

More

Resources

📖 Read the official README on GitHub

🐙 Browse open issues

🔍 Browse all 400+ MCP servers and Skills