TeamCity 5.X REST documentation directs us to a plug-ins page that is not TeamCity 5.X specific. I just recently realized this, and it seems that some of the functionality such as the running:true build dimension are not supported until TeamCity 6.0.
Does anyone know where I can find documentation about the REST API for TC 5.X for reference?
You can review older versions of the documentation but not based on the TeamCity release numbers. You might have some luck looking at versions prior to the 6.0 release on Dec. 1, 2010.