Documentation Skill

Purpose

Generate comprehensive, maintainable documentation including code docstrings, API specifications, architecture diagrams, README files, and clear code explanations.

Activation Triggers

Activate this skill when:

• User says "document this", "explain this code", "how does this work?"
• User mentions "README", "docs", or "documentation"
• After completing a feature or creating API endpoints
• User says "write comments for this"

Documentation Types

1. Code Documentation (Docstrings)

Goal: Clear, comprehensive function/class documentation

Key Components:

• Brief description (one line)
• Detailed explanation (purpose and behavior)
• Args/Parameters (types, constraints, examples)
• Returns (type and meaning)
• Example (realistic usage)
• Raises/Throws (error conditions)
• Note (implementation details)

Language-Specific Formats:

• Python: """triple quotes""", Args/Returns/Raises format
• JavaScript/TypeScript: JSDoc /** */, @param/@returns/@throws tags
• Java: Javadoc /** */, @param/@return/@throws tags
• C#: XML comments /// <summary>

2. API Documentation

Goal: Complete API reference for each endpoint

Required sections per endpoint:

• HTTP method and path
• Brief description
• Request schema (params, body with types and constraints)
• Success response (status code, schema, example)
• Error responses (status codes, error codes, messages)
• Example usage (cURL and/or language-specific)
• Security notes (auth, rate limits, etc.)

Template:

### METHOD /api/path

Description of what this endpoint does.

**Request:**
- `field` (type, required/optional): Description

**Response (200 OK):**
- `field` (type): Description

**Errors:** 400 (validation), 401 (auth), 429 (rate limit)

**Security:** Auth required, rate limit X req/min

3. Architecture Documentation

Goal: Clear system overview and component relationships

Required sections:

• Overview: System purpose and architecture style
• System Diagram: ASCII or Mermaid diagram showing components and connections
• Core Components: For each component: responsibility, functions, technology, scaling strategy
• Data Flow: Step-by-step flows for key operations
• Integration Points: External services and internal APIs
• Security Architecture: Authentication, authorization, data protection
• Performance: Caching strategy, database optimization, scaling strategy
• Monitoring: Metrics, logging, alerts

4. README Generation

Goal: Comprehensive project README

Essential Sections:

1. Title + one-line description - What problem it solves
2. Features - Key features as bullet list
3. Installation - Clone, install, configure, run
4. Usage - Basic code example
5. Configuration - Environment variables table (Variable, Description, Required)
6. Development - Test, lint, build commands
7. License

Optional Sections (add as needed):

• Demo/screenshots, API Reference, Project Structure, Deployment, Contributing

5. Code Explanations

Goal: Clear explanations of complex code

Process:

1. High-Level Purpose - What problem does this solve? Where does it fit?
2. Step-by-Step Logic - Break down into phases, explain each clearly
3. Key Algorithms/Patterns - Identify algorithms, explain approach, note complexity
4. Edge Cases - Unusual inputs handled, assumptions made, validation performed

Structure each explanation as:

• Purpose (what and why)
• How It Works (numbered steps with formulas/logic)
• Why This Approach (rationale and alternatives considered)
• Edge Cases Handled (list with explanations)

When to Document

Always Document:

• Public APIs and endpoints
• Complex algorithms
• Non-obvious logic
• Security-sensitive code
• Performance-critical sections
• Error handling strategies

Consider Documenting:

• Helper functions with multiple params
• Class constructors
• Configuration options
• Database schema

Don't Bother Documenting:

• Trivial getters/setters
• Self-explanatory code
• Temporary/experimental code

Best Practices

1. Write for Future You: Assume you'll forget everything in 6 months
2. Explain Why, Not What: Code shows what, docs explain why
3. Keep Examples Current: Update examples when code changes
4. Use Consistent Format: Follow language conventions
5. Be Concise: Every word should add value
6. Use Active Voice: "Returns user" not "User is returned"
7. Include Edge Cases: Document unusual inputs and outputs
8. Update With Code: Outdated docs are worse than no docs

Integration Points

• Works with spec-driven skill for feature documentation
• Works with review skill to verify docs exist
• Auto-triggered after feature completion

Notes

• Default to clear code over comments (code is always correct, comments lie)
• Good naming reduces need for documentation
• Complex logic deserves explanation
• APIs require comprehensive documentation
• When in doubt, document it