Princeton Allsearch error envelope

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://raw.githubusercontent.com/api-evangelist/princeton/refs/heads/main/json-schema/princeton-allsearch-error.json",
  "title": "Princeton Allsearch error envelope",
  "description": "Error body returned by the Princeton University Library Allsearch API. Not RFC 9457; a nested object carrying a machine-readable problem code and a human message. Derived from a live 400 response on 2026-08-19.",
  "x-provenance": {
    "generated": "2026-08-19",
    "method": "derived",
    "source": "https://allsearch-api.princeton.edu/search/catalog",
    "verified_against": "examples/princeton-allsearch-empty-query-400.json",
    "x-operator": "institution"
  },
  "type": "object",
  "required": ["error"],
  "properties": {
    "error": {
      "type": "object",
      "required": ["problem", "message"],
      "properties": {
        "problem": {
          "type": "string",
          "description": "Machine-readable problem code. Observed value: QUERY_IS_EMPTY. Princeton publishes no enumeration of the full set, so this is not constrained here.",
          "examples": ["QUERY_IS_EMPTY"]
        },
        "message": {
          "type": "string",
          "description": "Human-readable explanation.",
          "examples": ["The query param must contain non-whitespace characters."]
        }
      },
      "additionalProperties": true
    }
  },
  "additionalProperties": false
}