Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden, and it does disclose one genuinely useful behavioral trait: values stay hidden so later readers read blind. That is real context an agent cannot get from the schema. However, it never states that the operation is read-only, what happens if neither or both ids are supplied (required count is 0), or any error behavior, so the safety profile remains inferred.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.