Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so safety is covered. The description adds genuinely new context: the upstream source (Free Dictionary API via Wiktionary, CC BY-SA licensing) and a per-call cost of 1 credit, which matters for budgeting. It stops short of describing fallback behavior for unknown words or the shape/quantity of audio links.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.