I'm using the AllInstrumentSearchRequest to obtain RIC's starting from ISIN's. Question for my functional collegue is, since the request returns many RICs ( ie, FCA has, on same market, more than one RIC, one for the after hour and one for the regular exchange ) but, of course, the one on the regular exchange has more financial importance, is it possible to have the the search ordered with such a criteria?
The InstrumentSearch call will deliver all RICs. You can filter by Instrument Type Groups, that is all. The other API search calls are for specific asset classes, they have various filtering capabilities that depend on the asset class.
To retrieve only the primary RIC for an ISIN, use a TermsAndConditionsExtractionRequest request. This call is described in the REST API Tutorial 7. If you want to test it in Postman you can download the collection from the downloads tab.