Alright, I've found two possible solutions to this. One, delete the
Clientservices.bob ClientRegistry.blob file located in the Steam folder and then restart Steam. It may fail the first time (it did for me when I moved my Steam folder to an external HD), but if you try again it'll create the file you just deleted and update the game, which should cause the SDK to show in Tools.
Edit: My mistake, I had the wrong file name.
The other option is through 2K Greg. He
has stated to PM him with your user ID and he'll look into it.
I'd try the first option first.