I am using a developer tool, which can be downloaded from the website of Graphisoft:
http://www.graphisoft.com/support/developer/
But if you want to know what GDL code I use, just ask what you are looking for and I will be happy to answer. I also create Free custom GDL objects each month. Look at my post
http://archicad-talk.graphisoft.com/viewtopic.php?t=29941&highlight= to do a request.