Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the tool's simplicity (single optional parameter, no output schema), the description covers the essential aspects: what it does, when to use it, and the parameter's semantics. It lacks explicit return format details (e.g., array of objects, fields), but for a list-like retrieval tool, the description is mostly complete. A 4 is appropriate because it handles the low complexity well but leaves minor gaps (ordering, data shape).
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.