Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden of behavioral disclosure, but it only states that the tool returns aggregate statistics. It does not reveal whether the operation is read-only (though a GET is implied by the name), what the response format looks like, whether pagination exists, or what 'statistics' means precisely (e.g., counts, averages, distributions). This lack of context is a significant gap for an unannotated tool.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.