{
  "instruction": "Use correct HTTP status codes for each operation type",
  "relevant_when": "Agent creates or modifies a REST API endpoint",
  "context": "Status codes convey what happened without the client needing to parse the body. Using 200 for everything loses valuable semantic information.",
  "sources": [
    {
      "type": "file",
      "filename": "skills/api-design-patterns/SKILL.md",
      "tile": "tessl-labs/api-design-patterns@0.1.0"
    }
  ],
  "checklist": [
    {
      "name": "201-for-creation",
      "rule": "POST endpoints that successfully create a resource return 201 Created, not 200 OK",
      "relevant_when": "Agent builds a POST endpoint that creates a resource"
    },
    {
      "name": "204-for-deletion",
      "rule": "DELETE endpoints that successfully delete a resource return 204 No Content with no response body",
      "relevant_when": "Agent builds a DELETE endpoint"
    },
    {
      "name": "422-for-validation",
      "rule": "Validation errors (valid JSON but fails business rules) return 422 Unprocessable Entity, not 400 Bad Request",
      "relevant_when": "Agent builds an endpoint with input validation"
    },
    {
      "name": "409-for-conflict",
      "rule": "Duplicate resource or state conflict errors return 409 Conflict",
      "relevant_when": "Agent builds an endpoint where duplicate or conflicting resources are possible"
    },
    {
      "name": "404-for-not-found",
      "rule": "Requests for a resource that does not exist return 404 Not Found with an error envelope",
      "relevant_when": "Agent builds an endpoint that looks up a resource by ID"
    }
  ]
}