Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly/openWorld/non-destructive, and the description adds substantial context beyond that: the arena-ranking-v2 qualification rule (five decided trades), the exact scoring formula (realized PnL, open losses counted, Wilson 95% lower-bound weighting), the below-qualification and small-sample warning behavior, row contents, data-privacy scope, and the paper_execution_v1 cost disclosure. It loses a point because it advertises window values ('today'|'24h'|'3m') that the input schema's enum forbids, a factual inconsistency that could send an agent into an error.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.