Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a simple, zero-parameter, read-only list tool, the description covers the essential aspects: what it lists and the shape of the response. Given that there is no output schema, noting the raw array is helpful. It could be more complete by describing the type of items in the array, but this is a minor gap for such a straightforward tool.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.