Two different promises get conflated in this category: whether the API answers, and whether what it answers is current. They are reported separately because they fail separately.
The API answering is a normal uptime commitment measured monthly, excluding scheduled maintenance announced in advance.
Data currency is a distribution, not a promise. `/v1/sellers` reports median record age per seller, live. Any vendor that gives you a single freshness number for an entire index is describing a marketing position rather than a system.
Upstream sources go down. When one does, cached values still return with their real `observed_at`, so you can see the data is stale and decide for yourself. Silently serving stale data as fresh is the failure mode this design exists to avoid.
Include the `request_id` from the failing response. It is on every response and it is the only thing that identifies your exact call.