Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, indicating a safe read operation. The description adds valuable behavior: it explains that the tool returns an identifier, that partial matches are possible (by name), and that multiple results are likely when names repeat, guiding the user to prefer domain-based selection. This goes beyond annotations without contradicting them.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.