Forensic Gadgeteer is a rare Creature — Vedalken Artificer Detective card from Murders at Karlov Manor Promos (PMKM), collector number 57p. Current market price: $2.04 (foil $2.22), TCGplayer market prices via Scryfall.
Whenever you cast an artifact spell, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.") Activated abilities of artifacts you control cost {1} less to activate. This effect can't reduce the mana in that cost to less than one mana.