{
  "instruction": "Implement proper PATCH partial update semantics",
  "relevant_when": "Agent creates or modifies a PATCH endpoint",
  "context": "PATCH means partial update — only fields included in the request body should be modified. Fields not present in the request must remain unchanged. This is different from PUT which replaces the entire resource.",
  "sources": [
    {
      "type": "file",
      "filename": "skills/api-design-patterns/SKILL.md",
      "tile": "tessl-labs/api-design-patterns@0.1.0"
    }
  ],
  "checklist": [
    {
      "name": "partial-update-only-provided-fields",
      "rule": "PATCH endpoints only update fields that are present in the request body — fields not included in the request remain unchanged (not set to null or default)",
      "relevant_when": "Agent builds a PATCH endpoint for updating a resource"
    },
    {
      "name": "whitelist-updatable-fields",
      "rule": "PATCH endpoints whitelist the fields that can be updated rather than blindly spreading the request body into the database query",
      "relevant_when": "Agent builds a PATCH endpoint for updating a resource"
    },
    {
      "name": "return-full-updated-resource",
      "rule": "PATCH endpoints return the full updated resource in the response so the client has the current state",
      "relevant_when": "Agent builds a PATCH endpoint for updating a resource"
    }
  ]
}