Documentation

Technical Documentation Writing

This skill guides you through creating effective technical documentation that helps users understand, use, and contribute to your software.

When to use this skill

Use this skill when you need to:

• Write README files for projects
• Document APIs and interfaces
• Create architecture documentation
• Write inline code documentation
• Maintain project wikis or knowledge bases

Prerequisites

• Understanding of the target audience
• Knowledge of the system being documented
• Familiarity with documentation tools (Markdown, Sphinx, Docusaurus)
• Access to code and subject matter experts

Guidelines

Documentation Types

README.md - Project entry point

• Project description and purpose
• Installation instructions
• Quick start guide
• Links to detailed documentation
• Contribution guidelines

API Documentation - Interface reference

• Endpoint descriptions
• Request/response examples
• Authentication details
• Error codes and handling

Architecture Decision Records (ADRs) - Design decisions

• Context and problem statement
• Decision drivers
• Considered options
• Decision outcome
• Consequences

Code Comments - Inline explanations

• Why, not what (code shows what)
• Complex algorithms
• Non-obvious behavior
• Public API documentation

README Structure

# Project Name

Brief description of what the project does and its main purpose.

## Features

- Core feature 1
- Core feature 2
- Core feature 3

## Installation

```bash
# Clone the repository
git clone https://github.com/user/repo.git

# Install dependencies
npm install

# Configure environment
cp .env.example .env

Quick Start

# Run the application
npm start

Visit http://localhost:3000 to see the application.

Documentation

• API Reference
• Architecture
• Contributing

License

MIT

### API Documentation

**OpenAPI/Swagger Example**
```yaml
openapi: 3.0.0
info:
  title: Orders API
  version: 1.0.0
paths:
  /orders:
    post:
      summary: Create a new order
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              required: [customer_id, items]
              properties:
                customer_id:
                  type: integer
                  description: ID of the customer
                items:
                  type: array
                  items:
                    type: object
                    properties:
                      product_id:
                        type: integer
                      quantity:
                        type: integer
      responses:
        201:
          description: Order created successfully
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Order'

Code Documentation

Docstring Standards

def process_payment(order_id: int, amount: Decimal) -> PaymentResult:
    """
    Process a payment for the given order.
    
    Args:
        order_id: The unique identifier of the order
        amount: The payment amount (must be positive)
    
    Returns:
        PaymentResult containing transaction_id and status
    
    Raises:
        OrderNotFoundError: If the order doesn't exist
        InvalidAmountError: If amount is negative or zero
        PaymentGatewayError: If the payment processor fails
    
    Example:
        >>> result = process_payment(123, Decimal("99.99"))
        >>> print(result.status)
        'success'
    """

Documentation Principles

• Document intent, not implementation
• Keep examples runnable
• Update docs with code changes
• Use consistent terminology

Architecture Documentation

C4 Model Approach

1. Context Diagram - System in its environment
2. Container Diagram - High-level tech stack
3. Component Diagram - Major building blocks
4. Code Diagram - Detailed implementation

ADR Template

# ADR 001: Use PostgreSQL for Primary Database

## Status
Accepted

## Context
We need a relational database for our application data.

## Decision
We will use PostgreSQL as our primary database.

## Consequences
- Team familiarity with PostgreSQL
- ACID compliance for data integrity
- Need to manage database migrations

Documentation Best Practices

Writing Style

• Use active voice
• Be concise and specific
• Include code examples
• Use diagrams for complex concepts
• Define acronyms on first use

Maintenance

• Review docs with code reviews
• Version documentation with code
• Track documentation issues
• Regular cleanup of outdated content

Accessibility

• Use semantic Markdown
• Add alt text to images
• Ensure good contrast in diagrams
• Provide text alternatives

Examples

See the examples/ directory for:

• readme-template.md - Complete README template
• api-docs-example/ - API documentation samples
• adr-template.md - Architecture Decision Record format
• style-guide.md - Documentation style guidelines

References

• Documentation as Code
• Markdown Guide
• Diátaxis Framework
• Write the Docs
• C4 Model

Source: HelixDevelopment/HelixAgent — distributed by TomeVault.