mermaid

name: mermaid description: Create diagrams and visualizations using Mermaid syntax. Use when users request flowcharts, sequence diagrams, class diagrams, state diagrams, entity relationship diagrams, Gantt charts, pie charts, mindmaps, timelines, user journey maps, Git graphs, quadrant charts, or requirement diagrams. Also use when users want to visualize processes, workflows, systems, data structures, or relationships. license: MIT metadata: author: "Ikuma Yamashita" version: "1.0.0"

Mermaid Diagram Creation

Create diagrams using Mermaid's text-based syntax. Mermaid converts text definitions into visual diagrams.

Quick Start

1. Create a .mermaid file in /mnt/user-data/outputs/
2. Start with diagram type declaration
3. Add diagram-specific syntax
4. Use present_files to share the diagram

Diagram Types

Mermaid supports these diagram types:

• flowchart - Process flows, decision trees, workflows
• sequenceDiagram - Message exchanges, API interactions
• classDiagram - Object-oriented structures, UML
• stateDiagram-v2 - State machines, lifecycle diagrams
• erDiagram - Database schemas, data models
• gantt - Project timelines, schedules
• pie - Data distribution, percentages
• mindmap - Hierarchical concepts, brainstorming
• timeline - Historical events, roadmaps
• journey - User experiences, customer journeys
• gitGraph - Git branching, version control
• quadrantChart - Matrix analysis, prioritization
• requirementDiagram - Requirements and relationships

Syntax Structure

Basic Pattern

<diagram-type>
    <diagram content>

Every diagram begins with its type declaration, followed by content definitions.

Comments

Use %% for line comments:

flowchart LR
    %% This is a comment
    A --> B

Avoiding Syntax Breakers

Words to wrap in quotes:

• end - Can break flowcharts and sequence diagrams
• Nodes containing special characters or spaces

Patterns to avoid in comments:

• %%{ and }%% together - Similar to directives, confuses parser

Configuration Options

Frontmatter Configuration

Add YAML frontmatter before diagram definition:

---
title: Diagram Title
config:
  theme: forest
  look: handDrawn
  layout: elk
---
flowchart LR
    A --> B

Available Themes

• default - Standard Mermaid theme
• forest - Green color scheme
• dark - Dark background
• neutral - Minimal colors
• base - Clean, professional

Look Options

• classic - Traditional Mermaid style
• handDrawn - Sketch-like, informal appearance

Layout Algorithms

dagre (default)

• Classic layout
• Good balance of simplicity and clarity
• Ideal for most diagrams

elk (advanced)

• Sophisticated layout for complex diagrams
• Reduces overlapping
• Improves readability of large diagrams

Configure ELK with:

config:
  layout: elk
  elk:
    mergeEdges: true
    nodePlacementStrategy: LINEAR_SEGMENTS

Node placement strategies:

• SIMPLE
• NETWORK_SIMPLEX
• LINEAR_SEGMENTS
• BRANDES_KOEPF (default)

Diagram-Specific Syntax

For detailed syntax of specific diagram types, read the appropriate reference file:

• Flowcharts: references/flowchart.md
• Sequence diagrams: references/sequence-diagram.md
• Class diagrams: references/class-diagram.md
• State diagrams: references/state-diagram.md
• ER diagrams: references/entity-relationship-diagram.md
• Gantt charts: references/gantt-diagram.md
• Pie charts: references/pie-chart.md
• Mindmaps: references/mindmap.md
• Timelines: references/timeline.md
• User journeys: references/user-journey-diagram.md
• Git graphs: references/git-graph.md
• Quadrant charts: references/quadrant-chart.md
• Requirement diagrams: references/requirement-diagram.md

Common Patterns

Simple Flowchart

flowchart LR
    A[Start] --> B{Decision}
    B -->|Yes| C[Action 1]
    B -->|No| D[Action 2]
    C --> E[End]
    D --> E

Basic Sequence Diagram

sequenceDiagram
    participant A as Alice
    participant B as Bob
    A->>B: Hello Bob!
    B->>A: Hello Alice!

Entity Relationship Diagram

erDiagram
    CUSTOMER ||--o{ ORDER : places
    ORDER ||--|{ LINE-ITEM : contains
    CUSTOMER }|..|{ DELIVERY-ADDRESS : uses

Best Practices

1. Start simple - Begin with basic structure, add complexity as needed
2. Use descriptive labels - Make node/relationship names clear
3. Wrap special text - Quote text containing spaces or special characters
4. Add comments - Document complex logic or decisions
5. Configure appearance - Use themes and layouts for professional output
6. Test incrementally - Build diagram step-by-step to catch errors early
7. Keep it readable - Avoid overcrowding; split into multiple diagrams if needed

Workflow

1. Determine appropriate diagram type for user's needs
2. Read relevant reference file if needed for specific syntax
3. Create diagram with appropriate configuration
4. Save to /mnt/user-data/outputs/diagram.mermaid
5. Use present_files to share with user

Example with Configuration

---
title: System Architecture
config:
  theme: neutral
  look: handDrawn
  layout: elk
---
flowchart TB
    A[Client] --> B{Load Balancer}
    B --> C[Web Server 1]
    B --> D[Web Server 2]
    C --> E[(Database)]
    D --> E

This creates a hand-drawn style architecture diagram with ELK layout for optimal node placement.