Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Despite annotations already declaring readOnly, idempotent, and non-destructive, the description adds valuable behavioral detail: it strips scripts, styles, nav, ads, and comments, and converts specific HTML elements. This goes beyond annotations and gives the agent a clear mental model of the tool's output.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.