Copying fields between worksheets by eye is slow and easy to misalign. AI can build exact-match formulas. For this task, each Inventory row promises one Catalog record, so a returned value is safe only when the preserved key occurs exactly once. A missing key has no answer; a duplicate key can offer conflicting answers. Neither should be hidden behind the first result Excel happens to find. Other tasks may intentionally use one-to-many relationships, so uniqueness is a task rule rather than a universal property of every dataset.