FX rates

An FX rate set is a set of exchange rates an enterprise maintains. It is addressed by its fxrset_ identifier; rateSetCode is the natural key the enterprise chose at creation, unchangeable, and unique only within that enterprise.

Every rate is two-sided: bidRate applies when the customer sells the base currency and askRate when they buy it. The gap between them is the spread, which is why a single rate would not do.

Rates are decimal strings, not JSON numbers. A rate rounded to a double is a rate that does not reproduce.

crossCurrency is how a pair the set does not quote directly is priced. GET /fx-rate-sets/{fxRateSetId}/rates prices one pair and reports the legs it crossed through; the set read returns only the pairs the set quotes directly, so ask the sub-read rather than doing the arithmetic yourself.