It contains the call interface, and a trivial example, yet has left the end user to identify the useful information that should be documented. It appears that most of the MSDN api documentation has been autogenerated from the code. Which is completely useless when the names give no clue.
I have been looking at using the WF rules engine outside of the WF framework. This should be easy to do, yet the documentation sucks. You end up having to hunt around various blogs &c.