Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare the full safety profile (readOnlyHint, idempotentHint, destructiveHint=false, openWorldHint=false). The description adds meaningful behavior beyond that: the mode switch between list vs. semantic search, the source kinds (files, links, pasted text), and that search returns a grounded answer plus snippets.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.