Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With readOnlyHint/openWorldHint/destructiveHint=false already given, the description adds real context beyond the annotations: cloud-only requirement and the default search field set (sender+subject+body via Graph $search). It also explains performance tradeoffs ('faster, no body scan') for metadata scope, which is genuinely useful behavioral detail. It stops short of describing result shape or pagination, but the output schema covers returns, so this is a near-miss rather than a gap.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.