A shopping agent can execute a valid payment and still make a bad purchase. Imagine a buyer asks for two compact umbrellas, delivered to Singapore, within a total budget. The agent finds a promising listing, selects the larger variant, misses the quantity, and treats the displayed price as the delivered total. The wallet signs correctly. The payment succeeds. The buyer still gets the wrong outcome. This is a hypothetical example, not a customer story. It illustrates a useful boundary: ...