Omni-Tell wants to Show and Tell a huge threat like Omniscience or Atraxa, Grand Unifier straight into play, so Containment Priest is a premium answer since anything put into play this way (not cast) gets exiled outright. Mindbreak Trap is a cheap, often-free way to blow up their combo turn once they've cast multiple cheap cantrips like Ponder and Brainstorm. Surgical Extraction and Faerie Macabre give extra graveyard/plan disruption against their card selection engine. The equipment and Cloak and Dagger trim since this matchup is about proactive disruption and fast pressure before their turn-4 Show and Tell, so prioritize Thoughtseize, Thalia's tax, and our cheap threats to close the game quickly.