The format contains everything a Gerber File Set does, like images for all layers, drills, netlist, BOM. The information inside the IPC-2581 is strictly structured. Usually, there is no need to add anything, to fully and automatically define/understand the PCB and assembled components.
Thanks to included geometry data and netlist (the equivalent of IPC-356), ZofzPCB can create component models right from the start.
Most of the IPC-2581 files describe only logical stackup information. For example, if mechanical (thickness) information is inadequate, it might be needed to edit the thickness column in the stackup. Note - when you specify the total board thickness, using the <Profile> layer thickness entry, all missing core layers will be created automatically.