Documentation Skill

Maintain organized, well-structured project documentation. Prioritizes updating existing docs over creating new ones.

When to Use

• Creating or updating any project documentation
• Before creating a new doc file
• When documenting technical decisions, API flows, or architecture
• Writing changelogs, READMEs, or guides

Core Principles

1. Update First, Create Never (Unless Necessary)

Before creating any new doc:

1. Search docs/ for existing related documentation
2. Check if content belongs in an existing file
3. Only create new files for genuinely distinct topics

Existing docs always beat new docs.

2. Document Metadata Header

Every documentation file MUST include a YAML frontmatter header:

---
title: [Document Title]
created: YYYY-MM-DD
author: [Name or "AI-assisted"]
last_updated: YYYY-MM-DD
updated_by: [Name or "AI-assisted"]
status: [draft | active | deprecated]
---

Rules:

• created and author are set once, never changed
• last_updated and updated_by change on every edit
• status tracks document lifecycle

3. Minimal Document Count

4. Standard Doc Structure

docs/
├── architecture.md        # Technical patterns & decisions
├── technical-flows.md     # Mermaid diagrams & API flows
├── product-requirements.md  # PRD (if applicable)
├── [topic]-guide.md       # Only for major topics
└── competitive-analysis-[name].md  # Market research

Root-level docs (not in docs/):

• README.md — Project overview
• CHANGELOG.md — Version history
• TASKS.md — Sprint/backlog
• CONTRIBUTING.md — Contribution guide (if open source)

Mermaid Diagram Guidelines

Flowcharts (LR or TD)

flowchart LR
    A[User Action] --> B{Decision}
    B -->|Yes| C[Result A]
    B -->|No| D[Result B]

Sequence Diagrams

sequenceDiagram
    participant U as User
    participant A as App
    participant S as Server
    
    U->>A: Action
    A->>S: Request
    S-->>A: Response
    A-->>U: Update

State Diagrams

stateDiagram-v2
    [*] --> Idle
    Idle --> Loading: fetch
    Loading --> Success: data
    Loading --> Error: error
    Success --> Idle: reset
    Error --> Idle: retry

Best Practices

1. Label everything — Edges and nodes should be self-explanatory
2. Left-to-right for flows — Easier to read
3. Top-down for hierarchies — Natural reading order
4. Group related nodes — Use subgraphs for clarity
5. Keep it simple — Max 10-15 nodes per diagram

Updating Documentation Checklist

When updating any doc:

• Update last_updated date in header
• Update updated_by in header
• Remove outdated information (don't just add)
• Verify all links still work
• Check code samples are current
• Confirm mermaid diagrams render correctly

Document Discovery

Before creating a new doc, always run:

# List existing docs
ls -la docs/

# Search for related content
grep -ri "search term" docs/

# Find mermaid diagrams
grep -r "mermaid" docs/

Templates

New Section in Existing Doc

---

## [Section Title]

_Added: YYYY-MM-DD_

[Content...]

New Document (only when justified)

---
title: [Document Title]
created: YYYY-MM-DD
author: [Name or "AI-assisted"]
last_updated: YYYY-MM-DD
updated_by: [Name or "AI-assisted"]
status: draft
---

# [Title]

[One-line description]

---

## Overview

[Content...]

Anti-Patterns

Changelog Conventions

Follow Keep a Changelog format:

## [Unreleased]

### Added
- New feature description

### Changed
- Modified behavior

### Fixed
- Bug fix description

### Removed
- Deprecated feature

---

## [1.0.0] - YYYY-MM-DD

### Added
- Initial release features

Categories: Added, Changed, Deprecated, Removed, Fixed, Security

Quick Reference

License

MIT