The SP Remote API Explorer is pretty cool utility for developers.

https://visualstudiogallery.msdn.microsoft.com/26a16717-0c9a-4367-8dfd-bb09e7e2deb5?SRC=Home

The utility can be installed on the developer VM with SharePoint and Visual Studio. The utility pre requisite is you will need local SP farm with Visual Studio.

But once you have all required pre requisite then you can navigate to SP objects and its methods and properties to check what is supported by CSOM, REST & Silverlight Objects.