/v1, every error response is an RFC 9457 problem document
(application/problem+json) with a stable code you can branch on:
title is the same for every occurrence of a code; detail explains this
occurrence; instance is the request path.
Validation failures also carry errors[], one entry per invalid field. Each
entry has two string fields: pointer, a JSON Pointer (RFC 6901) into the
request the server received (/entries/0/region names a field in the body,
/limit a query parameter), and detail, what is wrong with that value.
Pointers address the request, never the stored row.
The deprecated unprefixed routes keep their original {"error": "..."} bodies.
Validation and request errors
invalid_request_body, validation_failed, invalid_pagination, immutable_field
Credential and tenancy errors
unauthenticated, organization_unavailable
Lookup and server errors
not_found, price_not_found, duplicate_price, rate_limited, internal_error