GTK-Doc is used to document C code. It is typically used to document the public API of libraries, such as the GTK+ and GNOME libraries, but it can also be used to document application code.
GTK-Doc has some special code to document the signals and properties of GTK+ widgets and GObject classes which other tools may not have.
These details are provided for information only. No information here is legal advice and should not be used as such.