Returns, for each requested destination country, the trip fields that are mandatory when creating a trip there: fields that are always required plus fields made required by a destination-country condition. Fields whose requiredness additionally depends on other field values at trip-creation time are flagged conditionallyRequired with their conditions included. Requiredness driven by compliance workflows or travel policies is not included — it depends on the origin country and traveler, not the destination alone. Fields flagged singleTravelerOnly are hidden on group trips but are still reported mandatory here — this endpoint has no traveler-count input to gate on.

Polling for changes (PROD-1723): pass since to narrow the response to fields touched after that timestamp — store the returned asOf and pass it back as since on your next poll. This is an approximate change feed, not a diff: a field can appear even if a specific country's required/not-required outcome is unaffected (only some other property changed). Deletions of a field or a conditional-requiredness rule leave no trace in since and are not reflected there.

Knowing when to reconcile (PROD-1783): every response also carries an opaque version for your whole mandatory-field configuration. Store it alongside asOf. When version is unchanged, nothing this endpoint reports has changed and no reconcile is needed; when it changes, re-poll without since (passing an explicit countries list, see below) for a full snapshot. Unlike since, version moves on deletions too, so this replaces reconciling blindly on a timer. Compare it for equality only — it is not a timestamp, is not ordered, and is not comparable against the version returned by other endpoints.