As long as the MAC Address isn't associated with a different device (which it shouldn't be in this case, since the devices are new), and it PXE Boots it should be picked up by the core server as having a task ready and waiting for it. There should be nothing else you need to do. That means that you will either need to request that your devices arrive with network boot as the default boot action, or you'll need to hit the network boot button on first startup, but outside of that it should be untouched.
The agent is not needed because the PXE Rep will be processing what boot options to pass, and the PXE Rep does have an agent and can get the information for that device.
Make sure your "Bare Metal" entries only have the device name and the MAC address. Just having those two parameters seems to work the best for me.