Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
readOnlyHint=true already tells the agent this is a safe read. The description adds the opaque claim of a 'bounded' lookup without stating the bound (limit, depth, or traversal distance) or whether a missing key errors or returns empty. With annotations carrying the safety profile, the remaining behavioral value is minimal.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.