Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a zero-parameter, no-token public getter, the description covers the essential context: what data is available, that it is public, and that authentication is not required. It does not describe output shape, but no output schema exists and the absence is not a serious gap for this simple read operation.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.