Ordered from best outcome to worst.
Details
okThe call succeeded and
dataholds the parsed result.no_dataThe source was reached and has nothing for this query, for example a 404 or an empty body. This is an answer, not a fault.
staleA cached value served past its freshness window.
rate_limitedThe source asked the caller to slow down, a 429.
timeoutThe request did not return in time.
skippedNot attempted, because the host's breaker is open or a caller-side budget was hit.
errorAnything else: a 5xx, a malformed body, a transport failure.