Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, non-destructive. The description adds valuable behavioral traits beyond this: 'Deterministic, no LLM, no key — gate-able in CI.' It also explains the algorithmic behavior (consensus, pairwise cosine, ROUGE-L composite, closest/outlier). No contradiction with annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.