Extending Konqueror

Hello

I am trying to learn how kdeaddons/konq-plugins/arkplugin
works.

Going well, I can build and install it, but the plugin is
never loaded
in Konqueror.
Right-clicking a .tar.gz file (for example) doens't yield
any extra menu items.

Clues?
How does Konqueror decide which plugins to load?