what sort of GUI commands are you talking about?
Things like the remote admin menu.
Some examples:
safe_cprintf(ent, PRINT_DIALOG, "You must be an OP to use this command.\n");
safe_cprintf(self, PRINT_DIALOG, "You are already on this team!\n");
safe_cprintf(self, PRINT_DIALOG, "Invalid team\n");
safe_cprintf(ent, PRINT_DIALOG, "Server does not have this map (%s).\n", mapname);