Agent skill

Mermaid Diagrams

Creating and refining Mermaid diagrams with live reload. An agent skill from veelenga/claude-mermaid.

MITAuto-check passedDevelopment

Install Mermaid Diagrams

skills CLI

$ npx skills add veelenga/claude-mermaid --skill mermaid-diagrams -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI

$ gh skill install veelenga/claude-mermaid mermaid-diagrams --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy

$ git clone --depth 1 https://github.com/veelenga/claude-mermaid.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/mermaid-diagrams .claude/skills/mermaid-diagrams && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Paste into Claude Code

Install the "mermaid-diagrams" agent skill from https://github.com/veelenga/claude-mermaid/tree/main/skills/mermaid-diagrams into .claude/skills/mermaid-diagrams/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "mermaid-diagrams", then confirm the skill loads.

Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

$skill-installer

$skill-installer install https://github.com/veelenga/claude-mermaid/tree/main/skills/mermaid-diagrams

Type this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.

skills CLI

$ npx skills add veelenga/claude-mermaid --skill mermaid-diagrams -a codex

Project install goes to .agents/skills/; add -g for ~/.codex/skills/.

GitHub CLI

$ gh skill install veelenga/claude-mermaid mermaid-diagrams --agent codex

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/veelenga/claude-mermaid.git skills-src && mkdir -p .agents/skills && cp -r skills-src/skills/mermaid-diagrams .agents/skills/mermaid-diagrams && rm -rf skills-src

Use ~/.agents/skills/ instead of .agents/skills for a personal install.

Codex skills documentation · loads skills from .agents/skills/

Paste into Codex

Install the "mermaid-diagrams" agent skill from https://github.com/veelenga/claude-mermaid/tree/main/skills/mermaid-diagrams into .agents/skills/mermaid-diagrams/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "mermaid-diagrams", then confirm the skill loads.

Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add veelenga/claude-mermaid --skill mermaid-diagrams -a cursor

Project install goes to .agents/skills/; add -g for ~/.cursor/skills/.

GitHub CLI

$ gh skill install veelenga/claude-mermaid mermaid-diagrams --agent cursor

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/veelenga/claude-mermaid.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/skills/mermaid-diagrams .cursor/skills/mermaid-diagrams && rm -rf skills-src

Use ~/.cursor/skills/ instead of .cursor/skills for a personal install.

Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/

Paste into Cursor

Install the "mermaid-diagrams" agent skill from https://github.com/veelenga/claude-mermaid/tree/main/skills/mermaid-diagrams into .cursor/skills/mermaid-diagrams/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "mermaid-diagrams", then confirm the skill loads.

Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

gemini skills install

$ gemini skills install https://github.com/veelenga/claude-mermaid.git --path skills/mermaid-diagrams

--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.

skills CLI

$ npx skills add veelenga/claude-mermaid --skill mermaid-diagrams -a gemini-cli

Project install goes to .agents/skills/; add -g for ~/.gemini/skills/.

GitHub CLI

$ gh skill install veelenga/claude-mermaid mermaid-diagrams --agent gemini-cli

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/veelenga/claude-mermaid.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/skills/mermaid-diagrams .gemini/skills/mermaid-diagrams && rm -rf skills-src

Use ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.

Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/

Paste into Gemini CLI

Install the "mermaid-diagrams" agent skill from https://github.com/veelenga/claude-mermaid/tree/main/skills/mermaid-diagrams into .gemini/skills/mermaid-diagrams/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "mermaid-diagrams", then confirm the skill loads.

Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

GitHub CLI

$ gh skill install veelenga/claude-mermaid mermaid-diagrams

Installs for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).

skills CLI

$ npx skills add veelenga/claude-mermaid --skill mermaid-diagrams -a github-copilot

Project install goes to .agents/skills/; add -g for ~/.copilot/skills/.

Manual copy

$ git clone --depth 1 https://github.com/veelenga/claude-mermaid.git skills-src && mkdir -p .github/skills && cp -r skills-src/skills/mermaid-diagrams .github/skills/mermaid-diagrams && rm -rf skills-src

Use ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.

GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/

Paste into GitHub Copilot

Install the "mermaid-diagrams" agent skill from https://github.com/veelenga/claude-mermaid/tree/main/skills/mermaid-diagrams into .github/skills/mermaid-diagrams/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "mermaid-diagrams", then confirm the skill loads.

GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add veelenga/claude-mermaid --skill mermaid-diagrams -a opencode

OpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.

GitHub CLI

$ gh skill install veelenga/claude-mermaid mermaid-diagrams --agent opencode

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/veelenga/claude-mermaid.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/skills/mermaid-diagrams .opencode/skills/mermaid-diagrams && rm -rf skills-src

Use ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.

OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/

Paste into OpenCode

Install the "mermaid-diagrams" agent skill from https://github.com/veelenga/claude-mermaid/tree/main/skills/mermaid-diagrams into .opencode/skills/mermaid-diagrams/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "mermaid-diagrams", then confirm the skill loads.

OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

Facts

Skill name: mermaid-diagrams
GitHub stars: 216
Token cost: ~1.3k tokens
SKILL.md length: 415 words
Files: 1
Skills in repo: 1
Repo updated: Oct 7, 2026
First seen: Oct 7, 2026
Licence: MIT

At a glance

Creating and refining Mermaid diagrams with live reload. An agent skill from veelenga/claude-mermaid.

Works in 3 steps: Create Initial Diagram: Use… → Iterative Refinement: Make improvements… → Save Final Version: Use mermaid_save…
Users want flowcharts
SKILL.md covers Core Workflow, Tool Usage, Diagram Types and Best Practices, plus 4 more sections
Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Mermaid Diagrams is an agent skill from veelenga/claude-mermaid. Creating and refining Mermaid diagrams with live reload. Use when users want flowcharts, sequence diagrams, class diagrams, ER diagrams, state diagrams, or any other Mermaid visualization. Provides best practices for syntax, styling, and the iterative workflow using mermaidpreview and mermaidsave tools.

Its SKILL.md is about 1.3k tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It sits in Development, covering Diagrams. It works with Mermaid and Model Context Protocol. The repository describes itself as: MCP Server to previewing mermaid diagrams with live reload. The licence is MIT.

When your agent uses it

Users want flowcharts
Sequence diagrams
Any other Mermaid visualization

Example prompts

“/mermaid-diagrams”

Requirements

Pre-approved tools (allowed-tools): mcp__mermaid__mermaid_preview, mcp__mermaid__mermaid_save

Workflow steps

3 steps, taken from the first numbered list in SKILL.md.

Create Initial Diagram: Use mermaid_preview to render and open the diagram with live reload
Iterative Refinement: Make improvements - the browser will auto-refresh
Save Final Version: Use mermaid_save when satisfied

What it can do on your machine

Read from SKILL.md and the folder at commit d4f8a89. It shows what the files ask for, not the result of running them.

Tool permissions
Pre-approves these tools, so the agent can use them without asking each time:
- mcp__mermaid__mermaid_preview
- mcp__mermaid__mermaid_save
From allowed-tools in the SKILL.md frontmatter.
Runs code
No scripts in the folder and no shell commands in SKILL.md (its code samples are mermaid).
From the folder's file list and the shell code blocks in SKILL.md.
Network
No URLs in SKILL.md.
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Mermaid Diagrams loads about 1.3k tokens when it runs. Until then it costs about 81 tokens; SKILL.md has 415 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it: ~81
When it runs · the whole SKILL.md, loaded when a task matches: ~1.3k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from veelenga/claude-mermaid at commit d4f8a89, republished under its MIT licence (© veelenga). 415 words, ~1,274 tokens.

Download SKILL.mdSave it as .claude/skills/mermaid-diagrams/SKILL.md (or your agent's skills folder).

name: mermaid-diagrams
description: Creating and refining Mermaid diagrams with live reload. Use when users want flowcharts, sequence diagrams, class diagrams, ER diagrams, state diagrams, or any other Mermaid visualization. Provides best practices for syntax, styling, and the iterative workflow using mermaid_preview and mermaid_save tools.
allowed-tools: mcp__mermaid__mermaid_preview, mcp__mermaid__mermaid_save

Mermaid Diagram Expert

You are an expert at creating, refining, and optimizing Mermaid diagrams using the MCP server tools.

Core Workflow

Create Initial Diagram: Use mermaid_preview to render and open the diagram with live reload
Iterative Refinement: Make improvements - the browser will auto-refresh
Save Final Version: Use mermaid_save when satisfied

Tool Usage

mermaid_preview

Always use this when creating or updating diagrams:

diagram: The Mermaid code
preview_id: Descriptive kebab-case ID (e.g., auth-flow, architecture)
format: Use svg for live reload (default)
theme: default, forest, dark, or neutral
background: white, transparent, or hex colors
width, height, scale: Adjust for quality/size

Key Points:

Reuse the same preview_id for refinements to update the same browser tab
Use different IDs for multiple simultaneous diagrams
Live reload only works with SVG format

mermaid_save

Use after the diagram is finalized:

save_path: Where to save (e.g., ./docs/diagram.svg)
preview_id: Must match the preview ID used earlier
format: Must match format from preview

Diagram Types

Flowcharts (`graph` or `flowchart`)

Direction: LR, TB, RL, BT

mermaid

graph LR
    A[Start] --> B{Decision}
    B -->|Yes| C[Action]
    B -->|No| D[End]

    style A fill:#e1f5ff
    style C fill:#d4edda

Sequence Diagrams (`sequenceDiagram`)

⚠️ Do NOT use style statements - not supported

mermaid

sequenceDiagram
    participant User
    participant App
    participant API

    User->>App: Login
    App->>API: Authenticate
    API-->>App: Token
    App-->>User: Success

Class Diagrams (`classDiagram`)

mermaid

classDiagram
    class User {
        +String name
        +String email
        +login()
    }
    class Order {
        +int id
        +Date created
    }
    User "1" --> "*" Order

Entity Relationship (`erDiagram`)

mermaid

erDiagram
    USER ||--o{ ORDER : places
    ORDER ||--|{ LINE_ITEM : contains

    USER {
        int id PK
        string email
        string name
    }

State Diagrams (`stateDiagram-v2`)

mermaid

stateDiagram-v2
    [*] --> Idle
    Idle --> Processing : start
    Processing --> Complete : finish
    Complete --> [*]

Gantt Charts (`gantt`)

mermaid

gantt
    title Project Timeline
    section Phase 1
    Task 1 :a1, 2024-01-01, 30d
    Task 2 :after a1, 20d

Best Practices

Preview IDs

Use descriptive names: architecture, auth-flow, data-model
Keep the same ID during refinements
Use different IDs for concurrent diagrams

Themes & Styling

default: Clean, professional
forest: Green tones
dark: Dark background
neutral: Grayscale

Use transparent background for docs, white for standalone

Common Patterns

System Architecture:

mermaid

graph TB
    Client[Web App]
    API[API Gateway]
    DB[(Database)]

    Client --> API --> DB

Authentication Flow:

mermaid

sequenceDiagram
    User->>App: Login Request
    App->>Auth: Validate
    Auth-->>App: JWT Token
    App-->>User: Access Granted

Show full SKILL.md (178 more words)Show less

User Interaction

When a user requests a diagram:

Clarify if needed: What type? What level of detail?
Choose diagram type:
- Process/workflow → Flowchart
- System interactions → Sequence
- Code structure → Class
- Database → ER
- Timeline → Gantt
Create with preview: Use descriptive preview_id, start with good defaults
Iterate: Keep same preview_id, explain changes
Save: Ask where/what format, use mermaid_save

Proactive Behavior

Always preview diagrams, don't just generate code
Use sensible defaults without asking
Reuse preview_id for refinements
Suggest improvements when you see opportunities
Explain your diagram type choice briefly

Common Issues

Syntax errors: Check quotes, arrow syntax, keywords Layout issues: Try different directions (LR vs TB) Text overlap: Increase dimensions or shorten labels Colors not working: Verify CSS color format; remember sequence diagrams don't support styles

Example Interaction

User: "Create an auth flow diagram"

You: "I'll create a sequence diagram showing the authentication flow." [Use mermaid_preview with preview_id="auth-flow"]

User: "Add database and error handling"

You: "I'll add database interaction and error paths." [Use mermaid_preview with same preview_id - browser auto-refreshes]

User: "Save it"

You: "Saving to ./docs/auth-flow.svg" [Use mermaid_save]

Files

Just SKILL.md in skills/mermaid-diagrams of veelenga/claude-mermaid.

Open the folder on GitHubat commit d4f8a89

Compare with similar skills

Mermaid Diagrams next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Mermaid Diagrams compared with similar skills
Skill	Stars	Used in	Tokens	Auto-check	Licence	Repo updated
Mermaid Diagrams this skillveelenga/claude-mermaid	216	—	~1.3k	Automated safety check: Pass	MIT	4 days ago
Excalidraw Skillyctimlin/mcp_excalidraw	2.5k	—	~4.6k	Automated safety check: Pass	MIT	yesterday
GitDiagram Repository Overviewahmedkhaleel2004/gitdiagram	18k	—	~427	Automated safety check: Pass	MIT	yesterday
Drawiobahayonghang/drawio-skills	287	—	~4.1k	Automated safety check: Notes	MIT	1 mo ago
Excalidraw Canvas Toolkitlingzhi227/agent-research-skills	390	—	~3.8k	Automated safety check: Pass	None	7 mo ago
Excalidraw Diagram DesignBV-Venky/excalidraw-architect-mcp	158	—	~1.6k	Automated safety check: Pass	MIT	1 mo ago

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Works with

Questions about Mermaid Diagrams

What does Mermaid Diagrams do?

Creating and refining Mermaid diagrams with live reload. An agent skill from veelenga/claude-mermaid. Mermaid Diagrams is an agent skill from veelenga/claude-mermaid. Creating and refining Mermaid diagrams with live reload.

When should I use Mermaid Diagrams?

Mermaid Diagrams fits situations like: users want flowcharts; sequence diagrams; any other Mermaid visualization.

How do I install Mermaid Diagrams in Claude Code?

Run `npx skills add veelenga/claude-mermaid --skill mermaid-diagrams -a claude-code`. Or copy the skill folder (skills/mermaid-diagrams in veelenga/claude-mermaid) into .claude/skills/mermaid-diagrams in your project. Claude Code loads it when a task matches its description.

How do I install Mermaid Diagrams in Codex?

Run `npx skills add veelenga/claude-mermaid --skill mermaid-diagrams -a codex`. Or copy the skill folder (skills/mermaid-diagrams in veelenga/claude-mermaid) into .agents/skills/mermaid-diagrams in your project. Codex loads it when a task matches its description.

Can I use Mermaid Diagrams in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add veelenga/claude-mermaid --skill mermaid-diagrams -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/mermaid-diagrams, .gemini/skills/mermaid-diagrams, .github/skills/mermaid-diagrams and .opencode/skills/mermaid-diagrams in your project.

What does Mermaid Diagrams need to run?

SKILL.md names no scripts, command-line tools or credentials: Mermaid Diagrams is instructions for the agent only. Its frontmatter pre-approves these tools: mcp__mermaid__mermaid_preview, mcp__mermaid__mermaid_save.

Does Mermaid Diagrams access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Mermaid Diagrams safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Mermaid Diagrams use?

Mermaid Diagrams is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Mermaid Diagrams use?

About 1.3k tokens (SKILL.md is roughly 5.1k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Mermaid Diagrams?

Skills that share tags, products or a category with Mermaid Diagrams: Excalidraw Skill (yctimlin/mcp_excalidraw, 2.5k stars), GitDiagram Repository Overview (ahmedkhaleel2004/gitdiagram, 18k stars), Drawio (bahayonghang/drawio-skills, 287 stars) and Excalidraw Canvas Toolkit (lingzhi227/agent-research-skills, 390 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Mermaid Diagrams?

veelenga (a GitHub user) maintains it in veelenga/claude-mermaid, which has 216 GitHub stars. The repository was last updated on October 7, 2026.

Source: veelenga/claude-mermaid on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.

Install Mermaid Diagrams

Facts

At a glance

What it does

When your agent uses it

Example prompts

Requirements

Workflow steps

What it can do on your machine

Tool permissions

Runs code

Network

Credentials

Context cost

Safety

SKILL.md

Mermaid Diagram Expert

Core Workflow

Tool Usage

mermaid_preview

mermaid_save

Diagram Types

Flowcharts (graph or flowchart)

Sequence Diagrams (sequenceDiagram)

Class Diagrams (classDiagram)

Entity Relationship (erDiagram)

State Diagrams (stateDiagram-v2)

Gantt Charts (gantt)

Best Practices

Preview IDs

Themes & Styling

Common Patterns

User Interaction

Proactive Behavior

Common Issues

Example Interaction

Files

Compare with similar skills

Similar skills

Excalidraw Skill

GitDiagram Repository Overview

Drawio

Excalidraw Canvas Toolkit

Excalidraw Diagram Design

Uml Diagrams

Related

Questions about Mermaid Diagrams

Flowcharts (`graph` or `flowchart`)

Sequence Diagrams (`sequenceDiagram`)

Class Diagrams (`classDiagram`)

Entity Relationship (`erDiagram`)

State Diagrams (`stateDiagram-v2`)

Gantt Charts (`gantt`)