From what I have found online and in the samba package, there is no good documentation for libsmbclient. This is an extremely useful library that will have lots of applications, but it is very hard to figure out the API only by looking at several small example programs.
The header file is quite well documented, you might want to give that a look.
Haven't heard back about this report. More documentation for the client libraries will be included in Samba4.