What fills [yourgame]Classes.h ?

I know it’s supposed to be the Header Tool thing, but In our project, _____Classes.h is empty.

Or Rather, it’s only got the below, what gives? I tried finding out more about the header tool but i either suck at searching (likely) or there isn’t a comprehensive doc. I am trying to absorb some code from the ShooterGame example, and the ShooterGamesClasses.h is filled with headers for the various classes. I don’t know how this is supposed to go down.

// Copyright 1998-2015 Epic Games, Inc. All Rights Reserved.
C++ class boilerplate exported from UnrealHeaderTool.
This is automatically generated by the tools.
DO NOT modify this manually! Edit the corresponding .h files instead!
#pragma once