Here is plugin::Slot, it returns the slot name from the id, such as slot 9999 is Powersource so it works like this:
Code:
quest::say("Your " . plugin::Slot(9999) . " slot contains " . quest::varlink($client->GetItemIDAt(9999)) . ".");
NPC says, 'Your Powersource slot contains Pure Energeian Elemental Orb.'
http://pastebin.com/R60Tbb5e