API Documentation¶

API documentation helps developers integrate with your services. It is often the primary interface between your product and technical users. Good API docs accelerate adoption; poor API docs drive developers to competitors.

Why API Docs Matter¶

Developers evaluate APIs partly through documentation:

• Can they understand what the API does?
• Can they get started quickly?
• Can they find answers to their questions?
• Can they trust the documentation is accurate?

API documentation directly affects developer adoption and satisfaction.

Types of API Documentation¶

Reference Documentation¶

Complete technical specification of the API:

• Endpoints and methods
• Request and response formats
• Parameters and data types
• Authentication
• Error codes

Reference docs answer: "What exactly does this endpoint do?"

Guides and Tutorials¶

Conceptual and task-oriented content:

• Getting started
• Authentication setup
• Common workflows
• Best practices

Guides answer: "How do I accomplish this goal?"

Code Examples¶

Working code developers can use:

• Request examples in multiple languages
• Full workflow examples
• SDK usage examples
• Copy-paste ready snippets

Examples answer: "What does the code look like?"

Reference Documentation Structure¶

Endpoint Documentation¶

Each endpoint needs complete documentation:

## Create User

Create a new user account.

### Endpoint

### Authentication

Requires API key with `users:write` scope.

### Request Body

| Field | Type | Required | Description |
|-------|------|----------|-------------|
| email | string | Yes | User's email address |
| name | string | Yes | User's display name |
| role | string | No | User role. Default: "viewer" |

### Example Request

```bash
curl -X POST https://api.example.com/v2/users \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "email": "user@example.com",
    "name": "Jane Smith",
    "role": "editor"
  }'

Response¶

Returns the created user object.

{
  "id": "usr_123abc",
  "email": "user@example.com",
  "name": "Jane Smith",
  "role": "editor",
  "created_at": "2024-01-15T10:30:00Z"
}

Error Responses¶

### Authentication Documentation

Explain how to authenticate:

```markdown
## Authentication

All API requests require authentication using an API key.

### Getting an API Key

1. Log in to your account
2. Go to **Settings > API Keys**
3. Click **Create New Key**
4. Select the required scopes
5. Copy the key (it won't be shown again)

### Using Your API Key

Include the key in the Authorization header:

```bash
curl https://api.example.com/v2/users \
  -H "Authorization: Bearer YOUR_API_KEY"

API Key Scopes¶

Security Best Practices¶

• Never commit API keys to version control
• Use environment variables for key storage
• Rotate keys regularly
• Use minimum required scopes

  ### Error Documentation
  
  Document error handling:
  
  ```markdown
  ## Errors
  
  The API uses standard HTTP status codes and returns detailed error objects.
  
  ### Error Response Format
  
  ```json
  {
    "error": {
      "code": "invalid_request",
      "message": "The request body is missing required field: email",
      "details": {
        "field": "email",
        "reason": "required"
      }
    }
  }
  

Common Error Codes¶

Rate Limiting¶

API requests are limited to 100 requests per minute per API key.

When rate limited, responses include:

HTTP/1.1 429 Too Many Requests
X-RateLimit-Limit: 100
X-RateLimit-Remaining: 0
X-RateLimit-Reset: 1642089600

Wait until the reset timestamp before retrying.

## Getting Started Content

### Quick Start Guide

Get developers to first successful request:

```markdown
## Quick Start

Make your first API call in under 5 minutes.

### 1. Get Your API Key

[Create an API key](#getting-an-api-key) in your account settings.

### 2. Make Your First Request

```bash
curl https://api.example.com/v2/me \
  -H "Authorization: Bearer YOUR_API_KEY"

3. View the Response¶

{
  "id": "usr_123abc",
  "email": "you@example.com",
  "name": "Your Name"
}

Congratulations! You've made your first API call.

Next Steps¶

• Create a user
• List all users
• Explore webhooks

  ### SDK Quick Starts
  
  Provide language-specific getting started:
  
  === "Python"
  
      ```python
      from acme import Client
  
      client = Client(api_key="YOUR_API_KEY")
  
      # Get current user
      me = client.users.me()
      print(f"Logged in as {me.name}")
      ```
  
  === "JavaScript"
  
      ```javascript
      import { AcmeClient } from '@acme/sdk';
  
      const client = new AcmeClient({ apiKey: 'YOUR_API_KEY' });
  
      // Get current user
      const me = await client.users.me();
      console.log(`Logged in as ${me.name}`);
      ```
  
  === "Go"
  
      ```go
      client := acme.NewClient("YOUR_API_KEY")
  
      // Get current user
      me, err := client.Users.Me(ctx)
      if err != nil {
          log.Fatal(err)
      }
      fmt.Printf("Logged in as %s\n", me.Name)
      ```
  
  ## Code Examples
  
  ### Example Quality
  
  Good examples are:
  
  - **Complete**: Can be copied and run
  - **Realistic**: Show actual use cases
  - **Correct**: Tested and working
  - **Commented**: Explain non-obvious parts
  
  ### Example Types
  
  **Basic examples** show single operations:
  
  ```python
  # Create a user
  user = client.users.create(
      email="user@example.com",
      name="Jane Smith"
  )
  

Complete examples show full workflows:

# Complete user onboarding workflow
import acme

client = acme.Client(api_key=os.environ["ACME_API_KEY"])

# Create the user
user = client.users.create(
    email="user@example.com",
    name="Jane Smith",
    role="editor"
)

# Add to a team
client.teams.add_member(
    team_id="team_456",
    user_id=user.id
)

# Send welcome email
client.emails.send(
    template="welcome",
    to=user.email,
    data={"name": user.name}
)

print(f"Created user {user.id} and added to team")

Interactive Documentation¶

API Explorers¶

Allow developers to try requests:

• Pre-filled with their API key
• Editable request parameters
• Live responses
• Copy-ready curl commands

Tools: Swagger UI, Redoc, ReadMe

Code Generation¶

Generate code from examples:

• Select endpoint
• Configure parameters
• Get code in preferred language

OpenAPI Specification¶

Specification-Driven Docs¶

Use OpenAPI (Swagger) as documentation source:

openapi: 3.0.0
info:
  title: Acme API
  version: 2.0.0
paths:
  /users:
    post:
      summary: Create a user
      description: Creates a new user account
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/CreateUserRequest'
      responses:
        '201':
          description: User created
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/User'

Benefits¶

• Single source of truth
• Generated documentation
• Generated client libraries
• Request validation
• Testing support

Maintenance¶

Version Documentation¶

Document API versions clearly:

• Current version
• Deprecated versions
• Breaking changes
• Migration guides

Change Documentation¶

Communicate changes effectively:

• Changelog for all changes
• Migration guides for breaking changes
• Advance notice for deprecations
• Clear timelines

Accuracy Verification¶

Keep docs accurate:

• Automated testing against examples
• CI/CD integration
• Regular review cycles
• User feedback integration

Developer Experience¶

Discoverability¶

Help developers find information:

• Clear navigation
• Effective search
• Related content links
• Index of endpoints

Consistency¶

Maintain consistent patterns:

• Same structure for all endpoints
• Consistent terminology
• Predictable locations

Completeness¶

Cover everything developers need:

• All endpoints documented
• All parameters explained
• All errors listed
• All edge cases addressed

Summary¶

API documentation determines developer success with your platform:

• Reference docs provide complete technical specification
• Guides explain concepts and workflows
• Examples show working code
• Interactive tools let developers experiment

Invest in API documentation as a critical part of developer experience.

Next: Release Notes covers documenting product changes.