Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and destructiveHint=false, so the safety profile is fully covered without the description. The description adds nothing beyond that — no disclosure of what 'bank details' contains, whether unknown SWIFT codes return empty or error, or whether responses are cached.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.