I think it is helpful to include documentation; that will (hopefully, if the documentation is well written) make it easier to figure out, if the user reads the documentation. (Devices and computer programs that do not have documentation are more difficult. Sometimes some of the functions can be figured out without too much difficulty (e.g. I have once figured out how to operate a radio scanner, even though most other people there could not figure it out (perhaps if they read the documentation (if they had it; I didn't have it so maybe they didn't either) they would figure it out and I would also figure it out more easily), and I have never operated a radio scanner before), but having good documentation is better.)