Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so safety is covered. The description adds genuine context the annotations do not: the provenance disclosure 'Results are first-party information, not an independent review', which tells the agent to treat the payload as promotional rather than neutral.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.