mermaid-diagrams

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Comprehensive guide for creating software diagrams using Mermaid syntax. Use when users need to create, visualize, or document software through diagrams including class diagrams (domain modeling, object-oriented design), sequence diagrams (application flows, API interactions, code execution), flowcharts (processes, algorithms, user journeys), entity relationship diagrams (database schemas), C4 architecture diagrams (system context, containers, components), state diagrams, git graphs, pie charts, gantt charts, or any other diagram type. Triggers include requests to "diagram", "visualize", "model", "map out", "show the flow", or when explaining system architecture, database design, code structure, or user/application flows.

3.4kinstalls

Sourcesoftaworks/agent-toolkit

Added on2026-02-04

NPX Install

npx skill4agent add softaworks/agent-toolkit mermaid-diagrams

SKILL.md Content

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Mermaid Diagramming

Create professional software diagrams using Mermaid's text-based syntax. Mermaid renders diagrams from simple text definitions, making diagrams version-controllable, easy to update, and maintainable alongside code.

Core Syntax Structure

All Mermaid diagrams follow this pattern:

mermaid

diagramType
  definition content

Key principles:

First line declares diagram type (e.g.,
```
classDiagram
```
,
```
sequenceDiagram
```
,
```
flowchart
```
)
Use
```
%%
```
for comments
Line breaks and indentation improve readability but aren't required
Unknown words break diagrams; parameters fail silently

Diagram Type Selection Guide

Choose the right diagram type:

Class Diagrams - Domain modeling, OOP design, entity relationships
- Domain-driven design documentation
- Object-oriented class structures
- Entity relationships and dependencies
Sequence Diagrams - Temporal interactions, message flows
- API request/response flows
- User authentication flows
- System component interactions
- Method call sequences
Flowcharts - Processes, algorithms, decision trees
- User journeys and workflows
- Business processes
- Algorithm logic
- Deployment pipelines
Entity Relationship Diagrams (ERD) - Database schemas
- Table relationships
- Data modeling
- Schema design
C4 Diagrams - Software architecture at multiple levels
- System Context (systems and users)
- Container (applications, databases, services)
- Component (internal structure)
- Code (class/interface level)
State Diagrams - State machines, lifecycle states
Git Graphs - Version control branching strategies
Gantt Charts - Project timelines, scheduling
Pie/Bar Charts - Data visualization

Quick Start Examples

Class Diagram (Domain Model)

mermaid

classDiagram
    Title -- Genre
    Title *-- Season
    Title *-- Review
    User --> Review : creates

    class Title {
        +string name
        +int releaseYear
        +play()
    }

    class Genre {
        +string name
        +getTopTitles()
    }

Sequence Diagram (API Flow)

mermaid

sequenceDiagram
    participant User
    participant API
    participant Database

    User->>API: POST /login
    API->>Database: Query credentials
    Database-->>API: Return user data
    alt Valid credentials
        API-->>User: 200 OK + JWT token
    else Invalid credentials
        API-->>User: 401 Unauthorized
    end

Flowchart (User Journey)

mermaid

flowchart TD
    Start([User visits site]) --> Auth{Authenticated?}
    Auth -->|No| Login[Show login page]
    Auth -->|Yes| Dashboard[Show dashboard]
    Login --> Creds[Enter credentials]
    Creds --> Validate{Valid?}
    Validate -->|Yes| Dashboard
    Validate -->|No| Error[Show error]
    Error --> Login

ERD (Database Schema)

mermaid

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

    USER {
        int id PK
        string email UK
        string name
        datetime created_at
    }

    ORDER {
        int id PK
        int user_id FK
        decimal total
        datetime created_at
    }

Detailed References

For in-depth guidance on specific diagram types, see:

references/class-diagrams.md - Domain modeling, relationships (association, composition, aggregation, inheritance), multiplicity, methods/properties
references/sequence-diagrams.md - Actors, participants, messages (sync/async), activations, loops, alt/opt/par blocks, notes
references/flowcharts.md - Node shapes, connections, decision logic, subgraphs, styling
references/erd-diagrams.md - Entities, relationships, cardinality, keys, attributes
references/c4-diagrams.md - System context, container, component diagrams, boundaries
references/architecture-diagrams.md - Cloud services, infrastructure, CI/CD deployments
references/advanced-features.md - Themes, styling, configuration, layout options

Best Practices

Start Simple - Begin with core entities/components, add details incrementally
Use Meaningful Names - Clear labels make diagrams self-documenting
Comment Extensively - Use
```
%%
```
comments to explain complex relationships
Keep Focused - One diagram per concept; split large diagrams into multiple focused views
Version Control - Store
```
.mmd
```
files alongside code for easy updates
Add Context - Include titles and notes to explain diagram purpose
Iterate - Refine diagrams as understanding evolves

Configuration and Theming

Configure diagrams using frontmatter:

mermaid

---
config:
  theme: base
  themeVariables:
    primaryColor: "#ff6b6b"
---
flowchart LR
    A --> B

Available themes: default, forest, dark, neutral, base

Layout options:

```
layout: dagre
```
(default) - Classic balanced layout
```
layout: elk
```
- Advanced layout for complex diagrams (requires integration)

Look options:

```
look: classic
```
- Traditional Mermaid style
```
look: handDrawn
```
- Sketch-like appearance

Exporting and Rendering

Native support in:

GitHub/GitLab - Automatically renders in Markdown
VS Code - With Markdown Mermaid extension
Notion, Obsidian, Confluence - Built-in support

Export options:

Mermaid Live Editor - Online editor with PNG/SVG export

Mermaid CLI -

npm install -g @mermaid-js/mermaid-cli

then

mmdc -i input.mmd -o output.png

Docker -

docker run --rm -v $(pwd):/data minlag/mermaid-cli -i /data/input.mmd -o /data/output.png

Common Pitfalls

Breaking characters - Avoid
```
{}
```
in comments, use proper escape sequences for special characters
Syntax errors - Misspellings break diagrams; validate syntax in Mermaid Live
Overcomplexity - Split complex diagrams into multiple focused views
Missing relationships - Document all important connections between entities

When to Create Diagrams

Always diagram when:

Starting new projects or features
Documenting complex systems
Explaining architecture decisions
Designing database schemas
Planning refactoring efforts
Onboarding new team members

Use diagrams to:

Align stakeholders on technical decisions
Document domain models collaboratively
Visualize data flows and system interactions
Plan before coding
Create living documentation that evolves with code

mermaid-diagrams

NPX Install

Tags

SKILL.md Content

Mermaid Diagramming

Core Syntax Structure

Diagram Type Selection Guide

Quick Start Examples

Class Diagram (Domain Model)

Sequence Diagram (API Flow)

Flowchart (User Journey)

ERD (Database Schema)

Detailed References

Best Practices

Configuration and Theming

Exporting and Rendering

Common Pitfalls

When to Create Diagrams