The path of the tpt.exe file on Jenkins (add "\tpt.exe" at the end). You can specifiy multiple paths as a comma seperated list. In that case the first existing path found will be used.
You can specify either an absolute path or a path relative to the workspace.
If this is a distributed build, so if you use an Agent to execute this task, make sure the path is in the context of the Agent machine and not the Master machine.