Dex Semantics adds declarations to your analytical models, which capture row meaning, join nature, how numbers add up, and decisional assumptions. Thanks to this, Dex scores 80% on ADE-bench with Claude Sonnet 5.5, compared to 73.3% without Dex (25% fewer tasks failed). Declarations live in your models as code, not a third-party tool. Dex then helps your agent convert declarations into your Semantic Layer of choice.