Jeskai Artifacts relies heavily on Urza's Saga fetching artifacts and Goblin Welder/Goblin Engineer reanimating artifacts from the graveyard; Grafdigger's Cage does not shut off Urza's Saga's chapter III search for noncreature artifacts, but more importantly it stops any creature recursion. Echoing Truth is versatile removal that bounces problematic permanents like Emry, Lurker of the Loch or a resolved Loki, God of Mischief, and can even bounce multiples if they've doubled up a nonlegendary permanent. Veil of Summer is nearly dead since this opponent plays no black spells and few blue spells target you offensively, so it's cut for more relevant answers. This matchup is largely a race, so keep your core Show and Tell into Omniscience plan intact.