Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations at all, the description carries the full burden, and it does disclose meaningful traits: the store is private, local, and encrypted, which matters for an agent deciding what to write. But it omits whether saves are deduplicated or overwritten, whether the write persists across sessions, any size limits, and what the call returns.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.