Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations only supply destructiveHint=false, so the description carries most of the burden and does add real behavioral context: it records history, returns ordered stage items, distinguishes manual vs auto items for succeeded semantics, and prescribes retry behavior on timeout. It does not say whether repeated reports for the same taskKey overwrite or append, nor what the returned structure looks like beyond 'ordered stage items'.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.