API Documentation

API Documentation

Patterns for creating clear, complete API documentation that developers can use without guessing.

Purpose

• Provide consistent structure for API endpoint documentation
• Ensure all critical information (auth, errors, examples) is included
• Enable developers to make successful API calls on first try

Core Patterns

Pattern 1: Endpoint Specification

When to use: Documenting any REST API endpoint.

Implementation:

## `METHOD /path/:param`

Brief description of what this endpoint does.

### Authentication
Bearer token required in Authorization header.

### Parameters
| Name | Type | In | Required | Description |
|------|------|-----|----------|-------------|
| id | string | path | Yes | Resource identifier |
| limit | integer | query | No | Max results (default: 20) |

### Request Body
```json
{
  "field": "value"
}

Response

{
  "id": "abc123",
  "created_at": "2024-01-01T00:00:00Z"
}

Errors

Example

curl -X GET "https://api.example.com/resource/abc123" \
  -H "Authorization: Bearer TOKEN"

**Benefits:**
- Developers find information predictably
- All edge cases documented upfront
- Copy-paste examples reduce errors

### Pattern 2: Error Response Documentation

**When to use:** Documenting error responses for any endpoint.

**Implementation:**
```markdown
### Error Response Format
All errors return this structure:
```json
{
  "error": {
    "code": "RESOURCE_NOT_FOUND",
    "message": "User with ID 'xyz' not found",
    "details": {
      "resource": "user",
      "id": "xyz"
    }
  }
}

Common Error Codes

**Benefits:**
- Consistent error handling in client code
- Actionable resolution guidance
- Reduces support burden

---

## Anti-Patterns

### Anti-Pattern 1: Missing Authentication Details

| Aspect | Description |
|--------|-------------|
| **WHY** | Developers waste time debugging 401 errors; increases support tickets |
| **DETECTION** | Endpoint docs without "Authentication" section; no example with auth header |
| **FIX** | Always include auth method, header format, and token example |

**Bad Example:**
```markdown
## GET /api/users

Returns list of users.

### Response
```json
[{"id": "1", "name": "John"}]

**Good Example:**
```markdown
## GET /api/users

Returns list of users.

### Authentication
Requires Bearer token in Authorization header.

Authorization: Bearer

### Response
```json
[{"id": "1", "name": "John"}]

Example

curl -X GET "https://api.example.com/api/users" \
  -H "Authorization: Bearer sk_live_abc123"

### Anti-Pattern 2: Undocumented Error States

| Aspect | Description |
|--------|-------------|
| **WHY** | Clients can't handle errors gracefully; leads to poor UX and debugging chaos |
| **DETECTION** | Docs only show success responses; no error codes or troubleshooting |
| **FIX** | Document every possible error with code, cause, and resolution |

**Bad Example:**
```markdown
### Response
```json
{"status": "success", "data": {...}}

**Good Example:**
```markdown
### Success Response (200)
```json
{"status": "success", "data": {...}}

Error Responses

### Anti-Pattern 3: Example-Free Documentation

| Aspect | Description |
|--------|-------------|
| **WHY** | Forces developers to guess; increases time to first successful call |
| **DETECTION** | No curl/code examples; no sample request/response pairs |
| **FIX** | Include complete, copy-paste-ready examples for every endpoint |

**Bad Example:**
```markdown
## POST /api/users
Creates a new user with the provided data.

Good Example:

## POST /api/users
Creates a new user.

### Request
```bash
curl -X POST "https://api.example.com/api/users" \
  -H "Authorization: Bearer TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"email": "user@example.com", "name": "John Doe"}'

Response

{
  "id": "usr_abc123",
  "email": "user@example.com",
  "name": "John Doe",
  "created_at": "2024-01-15T10:30:00Z"
}

---

## Validation Checklist

### Pre-Documentation
- [ ] Endpoint actually exists and works
- [ ] Understand all parameters and their validation
- [ ] Tested all error cases

### Documentation
- [ ] Authentication section included
- [ ] All parameters documented with types
- [ ] Request body example provided (if applicable)
- [ ] Success response example included
- [ ] Error responses documented with resolution
- [ ] Complete curl example provided

### Post-Documentation
- [ ] Example actually works when copied
- [ ] All status codes verified against implementation
- [ ] Cross-linked to related endpoints

---

## Related Resources

- Related skills: `skill_get("tutorial-patterns")`
- OpenAPI Specification: https://swagger.io/specification/

---

## Changelog

| Version | Date | Changes |
|---------|------|---------|
| 1.0 | 2026-01-13 | Initial version with anti-patterns |