r states the presence of a required field

The name of the payload and response objects can be changed to whatever suits the developers preference, 
as long as the references within the code are refactored.

foreignexchangelookuppost_payload  - type object
foreignexchangelookuppost_payload  Fields:
r	destinationCurrencyCode - type string
r	sourceCurrencyCode - type string
r	sourceAmount - type float * (or best representation of 12 digit number with up to 3 decimal places)
	markUpRate - type float *
	systemsTraceAuditNumber - type int *
	retrievalReferenceNumber - type string
	acquiringBin - type int *
	acquirerCountryCode - type int *
	cardAcceptor - type object
	
cardAcceptor Fields:	
	name - type string
	terminalId - type string
	idCode - type string
	address - type object

address Fields:
	city - type string
	state - type string
	county - type string
	country - type string
	zipCode - type string

foreignexchangelookuppost_response - type object
foreignexchangelookuppost_response Fields:
r	conversionRate - type float *
r	destinationAmount - type string 
	originalDestnAmtBeforeMarkUp - type string
	markUpRateApplied - type string

* You could in place of primitive types use type string to store all the non-object fields.
It is perfectly functional from a api querying stand-point, but may require adding methods that account for 
conversions into numbers, in later business logic.