I agree with these post, but I think that Nikolas give us the best option. Actually I use the "createService" rest service method on the root or desire ArcGIS Server folder. Like this...
http://servername:6080/arcgis/admin/services/foldername/createService
I use the attach json code to publish a tbx file. This tbx has a lot of tools that reference to many others python scripts. All of this are located into a registered folder to ensure that ArcGIS Server has permissions.
This process give me the best way to publish tbx.
Regards
Dani