Does a Semantic Knowledge Layer Make an Agent Measurably Better?

Give a frontier model raw SQL access to a warehouse and ask it for last quarter&rsquo;s top account by revenue. It will write clean SQL, execute it correctly, and hand you a confident answer that is wrong three different ways: it read a column of integer cents as dollars, it computed gross revenue when the house definition is net of discounts, and its &ldquo;quarter&rdquo; is the calendar quarter,…