Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description adds useful context beyond them: it specifies the data is 'public' (no auth implied) and warns to 'Preserve returned URLs exactly,' which is genuine behavioral guidance about handling the output.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.