The man pages for the RPM API are not contained in the system manpage directories, and are as such, not in the manpath. They are currently located in /usr/share/doc/rpm-devel-4.0.x/apidocs/man3 These should be moved to the proper location so that man can find them.
I disagree because 1) doxygen generated man pages are a bit frothy. For example, almost every function in rpm is documented, and doxygen spits a different man page for each. Overkill, IMHO. 2) the documentation is a bit flimsy, adding to /usr/share/man is just gonna create a mass of tedious bug reports about insignificant minutiae. 3) there are only a handful of people who are programming directly against rpmlib. Over 50% of those people are me, myself, and I, and I certainly don't need or want man pages in /usr/share/man I expect that the doxygen generated man pages will be ripped out at some point, possibly the apidocs as well. It's early yet ...