Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the behavioral burden. It discloses the ranking order (boosted first by decayed weight, then most recent) and the cost aspect ("Free to call"), which are valuable beyond the schema. However, it does not explicitly confirm read-only safety or mention side effects, though the verb "Return" suggests a non-mutating operation.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.