api-documentation-generator

API Documentation Generator

Overview

Automatically generate clear, comprehensive API documentation from your codebase. This skill helps you create professional documentation that includes endpoint descriptions, request/response examples, authentication details, error handling, and usage guidelines.

Perfect for REST APIs, GraphQL APIs, and WebSocket APIs.

When to Use This Skill

• Use when you need to document a new API
• Use when updating existing API documentation
• Use when your API lacks clear documentation
• Use when onboarding new developers to your API
• Use when preparing API documentation for external users
• Use when creating OpenAPI/Swagger specifications

How It Works

Step 1: Analyze the API Structure

First, I'll examine your API codebase to understand:

• Available endpoints and routes
• HTTP methods (GET, POST, PUT, DELETE, etc.)
• Request parameters and body structure
• Response formats and status codes
• Authentication and authorization requirements
• Error handling patterns

Step 2: Generate Endpoint Documentation

For each endpoint, I'll create documentation including:

Endpoint Details:

• HTTP method and URL path
• Brief description of what it does
• Authentication requirements
• Rate limiting information (if applicable)

Request Specification:

• Path parameters
• Query parameters
• Request headers
• Request body schema (with types and validation rules)

Response Specification:

• Success response (status code + body structure)
• Error responses (all possible error codes)
• Response headers

Code Examples:

• cURL command
• JavaScript/TypeScript (fetch/axios)
• Python (requests)
• Other languages as needed

Step 3: Add Usage Guidelines

I'll include:

• Getting started guide
• Authentication setup
• Common use cases
• Best practices
• Rate limiting details
• Pagination patterns
• Filtering and sorting options

Step 4: Document Error Handling

Clear error documentation including:

• All possible error codes
• Error message formats
• Troubleshooting guide
• Common error scenarios and solutions

Step 5: Create Interactive Examples

Where possible, I'll provide:

• Postman collection
• OpenAPI/Swagger specification
• Interactive code examples
• Sample responses

Examples

Example 1: REST API Endpoint Documentation

## Create User
 
Creates a new user account.
 
**Endpoint:**

Example 2: GraphQL API Documentation

Example 3: Authentication Documentation

Best Practices

✅ Do This

• Be Consistent - Use the same format for all endpoints
• Include Examples - Provide working code examples in multiple languages
• Document Errors - List all possible error codes and their meanings
• Show Real Data - Use realistic example data, not "foo" and "bar"
• Explain Parameters - Describe what each parameter does and its constraints
• Version Your API - Include version numbers in URLs (/api/v1/)
• Add Timestamps - Show when documentation was last updated
• Link Related Endpoints - Help users discover related functionality
• Include Rate Limits - Document any rate limiting policies
• Provide Postman Collection - Make it easy to test your API

❌ Don't Do This

• Don't Skip Error Cases - Users need to know what can go wrong
• Don't Use Vague Descriptions - "Gets data" is not helpful
• Don't Forget Authentication - Always document auth requirements
• Don't Ignore Edge Cases - Document pagination, filtering, sorting
• Don't Leave Examples Broken - Test all code examples
• Don't Use Outdated Info - Keep documentation in sync with code
• Don't Overcomplicate - Keep it simple and scannable
• Don't Forget Response Headers - Document important headers

Documentation Structure

Recommended Sections

1. Introduction

   • What the API does
   • Base URL
   • API version
   • Support contact

2. Authentication

   • How to authenticate
   • Token management
   • Security best practices

3. Quick Start

   • Simple example to get started
   • Common use case walkthrough

4. Endpoints

   • Organized by resource
   • Full details for each endpoint

5. Data Models

   • Schema definitions
   • Field descriptions
   • Validation rules

6. Error Handling

   • Error code reference
   • Error response format
   • Troubleshooting guide

7. Rate Limiting

   • Limits and quotas
   • Headers to check
   • Handling rate limit errors

8. Changelog

   • API version history
   • Breaking changes
   • Deprecation notices

9. SDKs and Tools

   • Official client libraries
   • Postman collection
   • OpenAPI specification

Common Pitfalls

Problem: Documentation Gets Out of Sync

Symptoms: Examples don't work, parameters are wrong, endpoints return different data Solution:

• Generate docs from code comments/annotations
• Use tools like Swagger/OpenAPI
• Add API tests that validate documentation
• Review docs with every API change

Problem: Missing Error Documentation

Symptoms: Users don't know how to handle errors, support tickets increase Solution:

• Document every possible error code
• Provide clear error messages
• Include troubleshooting steps
• Show example error responses

Problem: Examples Don't Work

Symptoms: Users can't get started, frustration increases Solution:

• Test every code example
• Use real, working endpoints
• Include complete examples (not fragments)
• Provide a sandbox environment

Problem: Unclear Parameter Requirements

Symptoms: Users send invalid requests, validation errors Solution:

• Mark required vs optional clearly
• Document data types and formats
• Show validation rules
• Provide example values

Tools and Formats

OpenAPI/Swagger

Generate interactive documentation:

Postman Collection

Export collection for easy testing:

Related Skills

• @doc-coauthoring - For collaborative documentation writing
• @copywriting - For clear, user-friendly descriptions
• @test-driven-development - For ensuring API behavior matches docs
• @systematic-debugging - For troubleshooting API issues

Additional Resources

• OpenAPI Specification
• REST API Best Practices
• GraphQL Documentation
• API Design Patterns
• Postman Documentation

Pro Tip: Keep your API documentation as close to your code as possible. Use tools that generate docs from code comments to ensure they stay in sync!