api-documenter — Claude Code skill: OpenAPI docs that hold up

---
name: api-documenter
description: API documentation specialist for OpenAPI/Swagger specifications. Use when documenting REST or GraphQL APIs.
allowed-tools: Read, Write, Edit, Bash, Grep, Glob
metadata:
  hooks:
    after_complete:
      - trigger: session-logger
        mode: auto
        reason: "Log documentation activity"
---

# API Documenter

Specialist in creating comprehensive API documentation using OpenAPI/Swagger specifications.

## When This Skill Activates

Activates when you:
- Ask to document an API
- Create OpenAPI/Swagger specs
- Need API reference documentation
- Mention "API docs"

## OpenAPI Specification Structure

```yaml
openapi: 3.0.3
info:
  title: API Title
  version: 1.0.0
  description: API description
servers:
  - url: https://example.com/api/v1
paths:
  /users:
    get:
      summary: List users
      operationId: listUsers
      tags:
        - users
      parameters: []
      responses:
        '200':
          description: Successful response
          content:
            application/json:
              schema:
                type: array
                items:
                  $ref: '#/components/schemas/User'
components:
  schemas:
    User:
      type: object
      properties:
        id:
          type: string
        name:
          type: string
```

## Endpoint Documentation

For each endpoint, document:

### Required Fields
- **summary**: Brief description
- **operationId**: Unique identifier
- **description**: Detailed explanation
- **tags**: For grouping
- **responses**: All possible responses

### Recommended Fields
- **parameters**: All parameters with details
- **requestBody**: For POST/PUT/PATCH
- **security**: Authentication requirements
- **deprecated**: If applicable

### Example

```yaml
/users/{id}:
  get:
    summary: Get a user by ID
    operationId: getUserById
    description: Retrieves a single user by their unique identifier
    tags:
      - users
    parameters:
      - name: id
        in: path
        required: true
        schema:
          type: string
        description: The user ID
    responses:
      '200':
        description: User found
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/User'
      '404':
        description: User not found
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/Error'
```

## Schema Documentation

### Best Practices

1. **Use references** for shared schemas
2. **Add descriptions** to all properties
3. **Specify format** for strings (email, uuid, date-time)
4. **Add examples** for complex schemas
5. **Mark required fields**

### Example

```yaml
components:
  schemas:
    User:
      type: object
      required:
        - id
        - email
      properties:
        id:
          type: string
          format: uuid
          description: Unique user identifier
          example: "550e8400-e29b-41d4-a716-446655440000"
        email:
          type: string
          format: email
          description: User's email address
          example: "[email protected]"
        createdAt:
          type: string
          format: date-time
          description: Account creation timestamp
```

## Authentication Documentation

Document auth requirements:

```yaml
security:
  - bearerAuth: []

components:
  securitySchemes:
    bearerAuth:
      type: http
      scheme: bearer
      bearerFormat: JWT
      description: Use your JWT token from /auth/login
```

## Error Responses

Standard error format:

```yaml
components:
  schemas:
    Error:
      type: object
      properties:
        error:
          type: string
          description: Error message
        code:
          type: string
          description: Application-specific error code
        details:
          type: object
          description: Additional error details
```

Common HTTP status codes:
- **200**: Success
- **201**: Created
- **204**: No Content
- **400**: Bad Request
- **401**: Unauthorized
- **403**: Forbidden
- **404**: Not Found
- **409**: Conflict
- **422**: Unprocessable Entity
- **500**: Internal Server Error

## Scripts

Generate OpenAPI spec from code:
```bash
python3 scripts/generate_openapi.py --name <resource-name> --output openapi.yaml
```

Validate OpenAPI spec:
```bash
python3 scripts/validate_openapi.py --input openapi.yaml
```

## References

- `references/openapi-template.yaml` - OpenAPI template
- `references/examples/` - API documentation examples
- [OpenAPI Specification](https://swagger.io/specification/)