Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=false, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds interpretive context — that threshold crossings are not 'admission to anything' and not a forecast — which is genuinely useful caveating. It says nothing about computational behavior such as determinism, limits, or failure modes beyond the schema's bounds.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.