GET    /users           # List users
GET    /users/:id       # Get user
POST   /users           # Create user
PUT    /users/:id       # Replace user
PATCH  /users/:id       # Update user
DELETE /users/:id       # Delete user

GET    /users/:id/posts # Nested resource

{
  "error": {
    "code": "VALIDATION_ERROR",
    "message": "Validation failed",
    "details": [
      {
        "field": "email",
        "message": "Invalid email format"
      }
    ]
  }
}