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name: api-design description: Design RESTful APIs with best practices. Use when creating new endpoints, designing API contracts, or reviewing API structures. allowed-tools: Read, Write, Edit, Grep, Glob

API Design Skill

Help design consistent, well-structured RESTful APIs.

Principles

URL Structure

• Use nouns for resources: /users, /orders
• Use plural forms: /users not /user
• Nest for relationships: /users/{id}/orders
• Keep URLs shallow (max 2-3 levels)

HTTP Methods

• GET: Read (idempotent, cacheable)
• POST: Create
• PUT: Full update (idempotent)
• PATCH: Partial update
• DELETE: Remove (idempotent)

Status Codes

• 200: Success
• 201: Created
• 204: No Content (successful DELETE)
• 400: Bad Request (client error)
• 401: Unauthorized
• 403: Forbidden
• 404: Not Found
• 409: Conflict
• 422: Unprocessable Entity (validation)
• 500: Server Error

Response Format

Copy{
  "data": { ... },
  "meta": {
    "page": 1,
    "total": 100
  },
  "errors": [
    { "field": "email", "message": "Invalid format" }
  ]
}

Pagination

• Use cursor-based for large datasets
• Use offset-based for simple cases
• Always include: page, per_page, total, next_cursor

Versioning

• URL prefix: /v1/users
• Header: Accept: application/vnd.api+json; version=1

Checklist for New Endpoints

• Clear resource naming
• Correct HTTP method
• Appropriate status codes
• Input validation
• Error response format
• Authentication required?
• Rate limiting needed?
• Documentation updated