The provenance problem
Many FX APIs resell an aggregated feed. When a customer or an auditor asks "where did this rate come from", the honest answer is "a reseller who got it from somewhere". Central banks publish their reference rates directly — the ECB, the US Federal Reserve, the State Bank of Pakistan, the Bank of England, the Bank of Canada — as public data, with no licence and a source you can name.
A bank is the authority for its own currency
The right rate for the pound comes from the Bank of England, not from a Canadian aggregator’s indicative view of sterling. LocaleSense serves each currency from the bank that is the authority for it, and every rate carries its source and as-of date.
Staleness, not silence
Central banks publish once a day on business days. A rate’s as-of date is the honest answer to "how fresh is this", and a source past its window is marked stale rather than served as current. A currency no source publishes is absent from the response — never a guessed number.
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