Integration with TFS 2015 on prem which includes the Rest API:
This is the first release that brings REST APIs to on-premises TFS.
|Release time frame|
There are now separate integrations for Visual Studio Online and Team Foundation Server, so you can integration with TFS on premise.
Note that you must be running Team Foundation Server 2015 or newer to use this integration since it uses the new REST API that was added in that version.