Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, destructiveHint=false, and idempotentHint=true, covering the safety profile. The description adds value by disclosing the bounded scope of returned data (aggregate counts, metadata, previews) and explicitly stating it never returns individual clinical data, which is not captured in annotations. This enriches the agent's understanding of what to expect.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.