From SRB

The routines that client programs can call are in the High Level Object API and the MCAT API.

There are also APIs used internally (Server to Server): the Low Level File API, the Low Level DB Large Object API, the Low Level DB Table Object API, and a Miscellaneous API.

All six of these API sets are described in the src/include/clStubExtern.h file, which includes comments that explain the arguments. In fact, the above two subpages are mostly just a cut and paste of sections of clStubExtern.h.