Foundry Inspector
Artifact Creature — Construct
Artifact spells you cast cost 
less to cast.
"Delicate resonance detectors could scan the assembly lines for metallic impurities, loose bolts, and freak occurrences of sentience." —Tawnos, proposal for overseer prototype
Jason A. Engle
Rulings
Once a player has announced an artifact spell, no player may take actions to try to remove Foundry Inspector from the battlefield before that spell's cost is locked in.
(wotc • 2016-09-20)
If an artifact spell has {X} in its mana cost, choose the value for X first, and then reduce the cost by {1}. For example, an artifact that costs {X} with X chosen as 4 costs {3} to cast if you control Foundry Inspector.
(wotc • 2016-09-20)
Rulings
Once a player has announced an artifact spell, no player may take actions to try to remove Foundry Inspector from the battlefield before that spell's cost is locked in.
(wotc • 2016-09-20)
If an artifact spell has {X} in its mana cost, choose the value for X first, and then reduce the cost by {1}. For example, an artifact that costs {X} with X chosen as 4 costs {3} to cast if you control Foundry Inspector.
(wotc • 2016-09-20)