Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description bears the full behavioral burden, and it does disclose two meaningful traits: it ignores caller data and costs nothing. It still omits other relevant behavior such as whether the output is deterministic, whether any auth is needed, or whether it has side effects, so the disclosure is only partial.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.