Ralph Schoon has posted a great reference, tutorial, and code on his personal blog which provides for A Rational Team Concert WorkItem Command Line! He provides code for a simple Work Item Command Line Client and explains the usage in a detailed but easily understood manner. Of course, noting that the post contains published code derived from examples from Jazz.net as well as the RTC SDK, we need to state that the usage of code from that example source code is governed by this license and as stated in the disclaimer, this code comes with the usual lack of promise or guarantee.
Since we have seen many requests to be able to create and update work items from a command line in the forum, as well as enhancement requests and a story for it in the RTC development repository, we wanted to highlight Ralph's work as a great starting point for creating these solutions. This WorkItemCommandLine should provide access for most of your automation needs when creating work items, as well as standing as a resource for the RTC work Item API.
So, go ahead and check out Ralph's blog post; we think you may find it stands as a hugely valuable resource as you move forward with your own RTC work!