It might be counter-intuitive but the back-end server treats mail, contacts, calendars, search, and mountpoints all like folders.
The createMountpoint command also refers to folders in its usage: createMountpoint(cm) [opts] {folder-name} {owner-id-or-name} {remote-item-id-or-path} -F/--flags <arg> flags -c/--color <arg> color -V/--view <arg> default type for folder.
We decided not to have an explosion of commands (renameSearchFolder, renameAddressBook, renameCalendar, renameTask, renameNotebook, renameBriefcase, renameMountpoint, deleteTask, deleteNotebook, deleteCalendar, modifyTaskColor, modifyCalendarColor, etc ,etc) and instead expose them all as ___Folder commands.