Markdown Mermaid Writing

Markdown Mermaid Writing is a community skill for creating technical diagrams in Markdown documents using Mermaid syntax, covering flowcharts, sequence diagrams, class diagrams, Gantt charts, and entity relationship diagrams for documentation workflows.

What Is This?

Overview

Markdown Mermaid Writing provides tools for embedding technical diagrams directly in Markdown files using Mermaid diagram syntax. It covers flowcharts that visualize process flows with decision nodes, parallel paths, and labeled connections, sequence diagrams that illustrate component interactions with messages, activations, and loops, class diagrams that represent code structures with inheritance, composition, and interface relationships, Gantt charts that display project timelines with task dependencies and milestone markers, and entity relationship diagrams that model data schemas with table relationships and cardinality. The skill enables developers to maintain diagrams alongside code in version-controlled documentation, ensuring diagrams evolve in sync with the systems they describe.

Who Should Use This

This skill serves software engineers writing technical documentation, architects creating system design documents, and technical writers producing developer guides with embedded diagrams. Teams practicing docs-as-code workflows will find particular value in keeping diagrams within the same repository as source code.

Why Use It?

Problems It Solves

Diagrams created in external tools become stale when code changes because updating requires opening separate applications. Binary image files in repositories cannot be diffed or reviewed in pull requests. Diagram tools with proprietary formats create vendor lock-in and require specific software for editing. Maintaining separate diagram files alongside Markdown documentation creates synchronization problems that lead to outdated visuals in published guides.

Core Highlights

Flowchart builder constructs process diagrams with decision logic and parallel paths. Sequence writer generates interaction diagrams with message flows between components. Class mapper creates code structure visualizations with relationships. Timeline planner builds Gantt charts with task dependencies and progress tracking.

How to Use It?

Basic Usage

%% Flowchart example
flowchart TD
  A[Start Request]
    --> B{Authenticated?}
  B -->|Yes| C[
    Process Request]
  B -->|No| D[
    Return 401]
  C --> E{Valid Data?}
  E -->|Yes| F[
    Save to Database]
  E -->|No| G[
    Return 400]
  F --> H[
    Return 200 Success]

%% Sequence diagram
sequenceDiagram
  participant U as User
  participant A as API
  participant D as Database
  U->>A: POST /items
  A->>A: Validate input
  A->>D: INSERT item
  D-->>A: item_id
  A-->>U: 201 Created

Real-World Examples

class MermaidGenerator:
  def __init__(self):
    self.lines = []

  def flowchart(
    self,
    direction:
      str = 'TD'
  ):
    self.lines = [
      f'flowchart '
      f'{direction}']
    return self

  def node(
    self,
    node_id: str,
    label: str,
    shape: str
      = 'rect'
  ):
    shapes = {
      'rect':
        (f'[{label}]'),
      'diamond':
        (f'{{{label}}}'),
      'round':
        (f'({label})')}
    s = shapes.get(
      shape,
      f'[{label}]')
    self.lines.append(
      f'  {node_id}{s}')
    return self

  def edge(
    self,
    from_id: str,
    to_id: str,
    label: str = None
  ):
    if label:
      self.lines.append(
        f'  {from_id}'
        f' -->|{label}|'
        f' {to_id}')
    else:
      self.lines.append(
        f'  {from_id}'
        f' --> {to_id}')
    return self

  def render(
    self
  ) -> str:
    return '\n'.join(
      self.lines)

Advanced Tips

Use subgraphs to group related nodes into labeled sections that represent system boundaries or service layers in architecture diagrams. For example, grouping all database nodes under a single subgraph clearly separates persistence concerns from application logic. Apply custom styling with classDef directives to color-code nodes by status or category. Combine multiple diagram types in a single document to show different perspectives of the same system, such as pairing a sequence diagram with a flowchart to cover both interaction order and process logic.

When to Use It?

Use Cases

Add an API request flow diagram to endpoint documentation in a Markdown README file. Create a database entity relationship diagram that lives alongside schema migration files. Build a deployment sequence diagram showing CI/CD pipeline stages and service interactions.

Related Topics

Mermaid diagrams, Markdown, technical documentation, flowcharts, sequence diagrams, architecture visualization, and diagrams as code.

Important Notes

Requirements

Markdown renderer with Mermaid support such as GitHub, GitLab, or compatible static site generators. Text editor for writing diagram syntax. Optional Mermaid CLI for local rendering and export to PNG or SVG formats.

Usage Recommendations

Do: keep diagrams focused on a single concept to maintain readability at rendered sizes. Use descriptive node labels that make diagrams understandable without surrounding text. Version diagrams alongside the code they document for synchronized updates.

Don't: create overly complex diagrams with too many nodes that become unreadable when rendered. Use diagram syntax features that are not supported by your target rendering platform. Rely on specific visual positioning since Mermaid auto-layouts diagrams.

Limitations

Auto-layout algorithms may not produce ideal node positioning for complex diagrams. Rendering support varies across different Markdown platforms and some environments require plugins or additional configuration steps. Diagram complexity is constrained by browser rendering performance for large node and edge counts.