Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, and non-destructive, so the safety profile is covered. The description adds value beyond that by disclosing the content scope of the read (timeline, tone, forward-looking statement counts, YoY shifts), giving the agent a sense of what it retrieves.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.