Foundry Inspector
Artifact Creature — Construct
Artifact spells you cast cost 
less to cast.
Automaton inspectors ensure that the Consulate's stringent standards for mass production are upheld.
Jason A. Engle
Commander Masters (CMM)
• #385Rulings
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)