Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Goes beyond the annotations by scoping what cannot be mutated and by disclosing that proposed changes come back as drafts and that long tasks emit progress before the final answer. Annotations only give readOnlyHint=false, destructiveHint=false and openWorldHint=true, so the 'returns drafts, mutates nothing' framing resolves real ambiguity. It stops short of covering auth needs, cost or latency expectations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.