The Tools packages are Ada related tools not written in Ada. As they are not written in Ada they do not need to be devided into GCC and GPL. The largest part of the tools is the Gtk+ support. Especialy the new GtkAda 2.8.1 needs a more current Gtk+ then some distributions provide. Apart from Gtk+ various development tools - like a vim editor and subversion - are provided.
Tools packages can and should be build and installed before the main GNAT packages are build or installed.
A tool package is not provided when the main distribution itself comes with a version which is current enough.