get_height gets which height, outer or inner? Are there error values, e.g. 0 as "don't know any height"? Does it have side effects? Is it a stable and reliable part of the API or bound to change soon? Is it thread safe? Will it change any of its parameters? Who deallocates the return value? Do you need to hold a lock somwhere?
Of course it might be a good idea to group together get_height, get_width, get_diagonal and get_depth if the above is all the same for those. But having no documentation just because you think it is trivial that get_height gets some height from somewhere just means that you are sloppy and didn't think of all of the above. So your code shouldn't be touched with a 10-foot-pole imho.
My solution, which I personally hate but know of no alternative to, is a documentation template for each function asking the above questions (depending on runtime and language of course) that I give people to fill in. Until they learn...