Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a zero-param, read-only, no-output-schema tool, the description tells the agent what it returns conceptually, that no auth is needed, and that results are cached. The one gap is any hint about the fields or ranking in the response, which an agent might want when deciding between this and its trending peers.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.