{
  "required": [
    "source_id",
    "canonical_locator",
    "etag",
    "last_modified",
    "fetch_status",
    "content_hash",
    "normalized_hash",
    "previous_snapshot_ref",
    "current_snapshot_ref",
    "diff_type",
    "semantic_change_class",
    "affected_claim_ids",
    "severity",
    "review_state",
    "review_owner",
    "next_check_at",
    "provenance"
  ],
  "optional_support": [
    "etag_strength",
    "conditional_request_used",
    "normalization_profile",
    "baseline_oracle_reuse"
  ]
}