Your workaround is correct - the syntax inside GMLiveAPI for functions is
func_name=call_flags (arguments) return_flags
Depending on what the functions do, call_flags can be : (call with self), :: (call with self and other), or ::: (call with self and other, or just self if other is a nonexistent instance ID).
I get arguments from fnames file in the runtime directory, but flags are set by hand so it’s not very hard to overlook something.