Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds value beyond these: it discloses the return content ('table title, dimension codes, and all available value codes with German labels') and the data licensing/authorization posture ('Swiss OGD, no auth, commercial use permitted'). No contradiction with annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.