| 400 | invalid_request | Request failed validation; error.details.fieldErrors names the fields |
| 400 | malformed_input, malformed_request | Body or query could not be interpreted |
| 400 | invalid_cursor, cursor_mismatch, cursor_expired | Cursor is not usable with this request |
| 401 | unauthorized, invalid_key | Missing, malformed or revoked key |
| 402 | insufficient_balance | Save a payment method in the portal to continue |
| 403 | wrong_scope, not_entitled, no_active_tenant, organization_required | Key or account cannot use this operation |
| 404 | not_found | Reference does not exist in the current publication |
| 404 | unknown_resource | Path is not one of the seven operations |
| 409 | request_replayed | Idempotency-Key already completed a request |
| 409 | request_id_mismatch | Same key reused for a different operation or caller |
| 409 | cursor_generation_changed | Data was republished between pages; restart |
| 413 | request_too_large | Body over 256 KiB |
| 422 | unsupported_filter | Filter not allowed on this facet or operation |
| 422 | unavailable | Reserved control used, for example projection: "fact_summary" |
| 429 | rate_limited | Over 6,000 requests per 60 s; honor retry_after_seconds |
| 503 | query_timeout | Exceeded the 12 s deadline; not charged; retryable |
| 503 | database_unavailable, service_unavailable, contract_unavailable | Transient Quoin failure; not charged; retryable |
| 503 | usage_accounting_unavailable | Billing could not be recorded, so the request was declined rather than miscounted; retryable |