In the newly released NetworkCalling feature in SDK 3.8.1, network calling metadata is attached via an explicit separate argument to StoreProgram(). Unfortunately, due to this way of working, UASM is unable to actually assign this metadata on its own.
It would be useful to have a dedicated section (as in code section, data section, "networkcalling" section?) for defining this metadata - looking at the current implementation, I don't see any reason why this can't be put into UASM.