Update note says: Only one field can be sorted on, and only if there is a suitable index, if there is no suitable index the request will fail.
I would vote for the ability to extend this functionality too.
For example retrieving a specific record as:
/api/1/TRVc/201/10000014
or /api/1/TRVc?sort=Number&range=range=201,10000014:201,10000020
to retrieve a range of transactions with IntYc=201 and 10000014<=Number<=10000020
i.e., compound index fields are separated by a slash and fields must be in the order of the key definition:
MainKeyBegin(Number,0);
KeySegment(IntYc);
KeySegment(Number);