Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The description goes well beyond the readOnly/destructive annotations by explaining how classifications are derived, what 'surprise' and 'vs_consensus' mean, the directional rather than verdict-like nature of hot/cool labels, the meaning of 'n/a', and the stable age_days semantics across re-requests. This is rich, non-obvious behavioral context.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.