Learn from the examples showing how to create function strings.
Example for rs_begin Function String
create function string rs_begin for gateway_func_class output rpc 'execute begin_xact'
Example for rs_insert Function String.
create function string publishers_rep.rs_insert for rs_sqlserver_function_class output rpc 'execute insert_publisher @pub_id = ?pub_id!new?, @pub_name = ?pub_name!new?, @city = ?city!new?, @state = ?state!new?'