Rails Technical Writer

Create clear, comprehensive documentation for Rails applications.

When to Use This Skill

• Writing or updating README.md
• Documenting API endpoints
• Creating setup/installation guides
• Writing architectural decision records (ADRs)
• Documenting complex features or workflows
• Adding inline code documentation
• Creating migration guides
• Documenting deployment processes

Quick Templates

README.md

# Project Name

Brief description of what the application does.

## Features

- User authentication with email confirmation
- Role-based authorization (admin, user)
- Real-time notifications with Turbo Streams

## Tech Stack

- **Framework**: Ruby on Rails 7.1
- **Database**: PostgreSQL 15
- **Frontend**: ViewComponent, Hotwire, Tailwind CSS
- **Background Jobs**: Solid Queue
- **Testing**: RSpec, FactoryBot, Capybara

## Prerequisites

- Ruby 3.3.0
- PostgreSQL 15+
- Node.js 20+

## Setup

Install dependencies

bundle install yarn install

Database setup

bundle exec rails db:create db:migrate

Start server

bin/dev

## Testing

bundle exec rspec

## License

[MIT License](LICENSE)

API Endpoint Documentation

# @api public
# @endpoint GET /api/v1/users
# @description List all users with pagination
#
# @param [Integer] page Page number (default: 1)
# @param [Integer] per_page Items per page (default: 25)
#
# @response 200 [Array<User>] List of users
# @response_example
#   {
#     "users": [
#       { "id": 1, "name": "John", "email": "[email protected]" }
#     ],
#     "meta": { "current_page": 1, "total_pages": 10 }
#   }
#
# @error 401 Unauthorized
# @error 422 Invalid parameters
def index
  @users = policy_scope(User).page(params[:page])
  render json: UsersSerializer.new(@users)
end

Architecture Decision Record (ADR)

# ADR 001: Use ActiveInteraction for Business Logic

## Status
Accepted

## Context
We need a pattern for encapsulating business logic with:
- Clear input/output contracts
- Built-in validation
- Composability
- Testability

## Decision
Use ActiveInteraction for all business logic operations.

## Consequences

### Positive
- Built-in type checking and validation
- Self-documenting interface
- Composable via `compose` method
- Consistent error handling

### Negative
- Additional gem dependency
- Team needs to learn new pattern

## Implementation
- Add `gem "active_interaction"` to Gemfile
- Create interactions in `app/interactions/`
- Follow naming: `Namespace::Verb` (e.g., `Users::Create`)

## Examples
See `app/interactions/users/create.rb`

Code Documentation

# Processes a payment and updates order status.
#
# Steps:
# 1. Validates payment method is active
# 2. Charges the payment gateway
# 3. Updates order status to "paid"
# 4. Sends confirmation email
#
# @param order [Order] The order to process
# @param payment_method [PaymentMethod] Payment method to charge
# @return [Boolean] true if successful
# @raise [PaymentGatewayError] if gateway unavailable
#
# @example
#   processor.process_payment(order, payment_method)
#
def process_payment(order, payment_method)
  return false unless payment_method.active?

  result = gateway.charge(
    amount: order.total,
    source: payment_method.token
  )

  if result.success?
    order.update!(status: :paid)
    OrderMailer.payment_confirmation(order).deliver_later
    true
  else
    order.errors.add(:base, result.error_message)
    false
  end
end

Documentation Best Practices

Writing Style

✅ Do:

• Use active voice: "The system validates..."
• Be concise: "Creates a user" not "This method creates a user record"
• Include examples with code snippets
• Structure with clear headings
• Keep documentation updated

❌ Avoid:

• Passive voice
• Outdated information
• Obvious comments: i++ // increment i
• Commented-out code (use git instead)

When to Add Comments

Comment:

• ✓ Why, not what (explain reasoning)
• ✓ Complex algorithms or business logic
• ✓ Workarounds for bugs
• ✓ Performance optimizations
• ✓ Security considerations
• ✓ Public API methods

Don't comment:

• ✗ Obvious code
• ✗ Redundant information
• ✗ Changelog info (use git)

README Structure

Essential sections (in order):

1. Project name + description
2. Features - What it does
3. Tech stack - Technologies used
4. Prerequisites - Requirements
5. Setup - Installation steps
6. Usage - How to run
7. Testing - How to test
8. Deployment - How to deploy
9. Contributing - Guidelines
10. License - Legal info

Feature Documentation

# Feature Name

## Overview
Brief description of the feature.

## Implementation

### Key Components
- `Model` - Handles data
- `Interaction` - Business logic
- `Controller` - HTTP interface

### How It Works

1. User performs action
2. Controller calls interaction
3. Interaction validates and processes
4. Result returned to user

## Usage

Example code

result = Features::DoSomething.run(params)

## Testing

RSpec.describe Features::DoSomething do it "works correctly" do # test code end end

## Gotchas

- Important consideration #1
- Important consideration #2

Documentation Checklist

When making changes, update:

• README.md (if features/setup changed)
• API docs (if API endpoints changed)
• Inline comments (for complex logic)
• ADR (for architectural decisions)
• CHANGELOG (for all user-facing changes)
• Migration guide (for breaking changes)

OpenAPI/Swagger Format

# swagger/v1/swagger.yaml
openapi: 3.0.0
info:
  title: MyApp API
  version: 1.0.0

paths:
  /api/v1/users:
    get:
      summary: List users
      parameters:
        - name: page
          in: query
          schema:
            type: integer
            default: 1
      responses:
        '200':
          description: Successful
          content:
            application/json:
              schema:
                type: object
                properties:
                  users:
                    type: array
                    items:
                      $ref: '#/components/schemas/User'

components:
  schemas:
    User:
      type: object
      properties:
        id:
          type: integer
        name:
          type: string
        email:
          type: string

Markdown Conventions

Use consistent formatting:

• # H1 for main title
• ## H2 for sections
• ### H3 for subsections
• `ruby for code blocks with syntax
• bold for emphasis
• - bullet for unordered lists
• 1. number for ordered lists
• [link text](url) for links

YARD Documentation (Ruby)

# @!group User Management

# Creates a new user account
# @param [Hash] attributes User attributes
# @option attributes [String] :email User email
# @option attributes [String] :password User password
# @return [User, nil] Created user or nil
# @raise [ValidationError] if invalid
def create_user(attributes)
  # implementation
end

# @!endgroup

Good vs Bad Examples

Good Documentation

## Email Verification Flow

When a user registers:

1. User submits registration form
2. System creates user with `confirmed_at: nil`
3. System generates unique confirmation token
4. System sends confirmation email with link
5. User clicks link in email
6. System verifies token and sets `confirmed_at`

**Security notes:**
- Tokens expire after 24 hours
- Tokens are single-use only
- Rate limiting applied

Bad Documentation

## Email stuff

User gets email. Click link. Done.

Reference Documentation

For comprehensive templates and detailed examples:

• Full documentation guide: technical-writing-reference.md (complete templates, setup guides, all platforms)

Remember: Good documentation is:

• Clear - Easy to understand
• Complete - All necessary information
• Current - Reflects actual code
• Concise - No unnecessary detail
• Consistent - Follows same structure