Authentication documentation determines whether developers successfully integrate with your API. According to research from Swagger's API documentation study, authentication sections receive more developer attention than any other documentation. Clear authentication documentation accelerates integration and reduces support burden by up to 70%.
What Must Authentication Documentation Include?
Every auth section must answer 5 essential questions:
Authentication Documentation Checklist
| # | Question | Example Answer |
|---|---|---|
| 1 | What method? | "This API uses Bearer token authentication with JWT" |
| 2 | Where to get credentials? | "Generate API keys in Dashboard → Settings → API Keys" |
| 3 | How to include in requests? | "Add header: Authorization: Bearer YOUR_TOKEN" |
| 4 | What's the exact format? | "Bearer" prefix required, space before token |
| 5 | What errors to expect? | 401 for invalid, 403 for insufficient permissions |
How to Document API Key Authentication
API key authentication is simplest. Use this template:
## Authentication This API uses API key authentication. Include your API key in every request. ### Getting Your API Key 1. Log in to your dashboard at dashboard.example.com 2. Navigate to Settings → API Keys 3. Click "Generate New Key" 4. Copy the key (it won't be shown again) ### Using Your API Key Include the key in the Authorization header: ``` Authorization: Bearer YOUR_API_KEY ``` ### Example Request ```bash curl https://api.example.com/v1/users \ -H "Authorization: Bearer sk_live_abc123def456" ``` ### Security Best Practices - Never commit API keys to version control - Store keys in environment variables - Rotate keys quarterly - Use separate keys for development and production
How to Document OAuth 2.0 Authentication
OAuth requires step-by-step flow documentation:
OAuth 2.0 Documentation Template
| Step | Endpoint | What Happens |
|---|---|---|
| 1. Authorize | GET /oauth/authorize | Redirect user for consent |
| 2. Callback | Your redirect_uri | Receive authorization code |
| 3. Exchange | POST /oauth/token | Trade code for access token |
| 4. Refresh | POST /oauth/token | Get new token when expired |
For each step, provide complete request and response examples:
### Step 1: Authorization Request
Redirect users to:
```
https://api.example.com/oauth/authorize?
client_id=YOUR_CLIENT_ID&
redirect_uri=https://yourapp.com/callback&
response_type=code&
scope=read:users write:users
```
### Step 3: Token Exchange
```bash
curl -X POST https://api.example.com/oauth/token \
-d "grant_type=authorization_code" \
-d "code=AUTH_CODE_FROM_CALLBACK" \
-d "client_id=YOUR_CLIENT_ID" \
-d "client_secret=YOUR_CLIENT_SECRET" \
-d "redirect_uri=https://yourapp.com/callback"
```
**Response:**
```json
{
"access_token": "eyJhbGciOiJIUzI1NiIs...",
"token_type": "Bearer",
"expires_in": 3600,
"refresh_token": "def502003fa..."
}
```
How to Document JWT Authentication
JWT documentation needs specific details about token structure:
## JWT Authentication
### Obtaining a JWT
POST /auth/login with credentials:
```bash
curl -X POST https://api.example.com/auth/login \
-H "Content-Type: application/json" \
-d '{"email": "user@example.com", "password": "your_password"}'
```
**Response:**
```json
{
"token": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...",
"expires_at": "2025-12-05T12:00:00Z"
}
```
### Using the JWT
```
Authorization: Bearer eyJhbGciOiJIUzI1NiIs...
```
### Token Structure
- **Algorithm:** HS256
- **Expiration:** 1 hour from issue
- **Claims:** user_id, email, roles, exp, iat
### Token Refresh
Call POST /auth/refresh before expiration with current token.
How to Document Authentication Errors
Authentication Error Reference
| Status | Error | Cause | Solution |
|---|---|---|---|
| 401 | Unauthorized | Invalid or missing credentials | Check API key format, verify not expired |
| 403 | Forbidden | Valid credentials, insufficient permissions | Request additional scopes or permissions |
| 429 | Too Many Requests | Rate limit exceeded | Wait and retry, implement backoff |
Frequently Asked Questions About Auth Documentation
Should I document both success and failure cases?
Yes—always include error responses. Show what happens with valid credentials AND invalid credentials. Developers encountering errors need documentation explaining what went wrong. Error documentation is as important as success documentation.
How many code examples should I provide?
At minimum: curl, plus 2-3 common languages. curl examples are universal. Then add JavaScript/Node.js, Python, and your API's primary audience language. More examples serve more developers.
Should I explain HTTPS requirements?
Yes, explicitly. "All API requests must use HTTPS. HTTP requests will be rejected." Authentication over HTTP exposes credentials. Make the requirement crystal clear.
How do I test my auth documentation?
Have someone unfamiliar with your API follow the docs. Watch where they struggle. Those pain points need improvement. Run every code example yourself—broken examples destroy credibility.
Can AI help write authentication docs?
Yes, AI tools like River's API Documentation Writer can generate comprehensive auth documentation. Input your authentication method and endpoints, and the AI creates complete documentation with examples, error handling, and security guidance.
Authentication documentation directly affects API adoption and integration success. Document clearly, completely, and with extensive examples. Cover all auth types, security requirements, and error cases. Use River's API Documentation tools to write clear authentication flow documentation automatically.