Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a low-complexity one-parameter tool, the description covers the essential behavior, lists the expected return fields, and notes the caching behavior. Since no output schema exists, enumerating admin_district, ward, constituency, LSOA, NUTS, and coordinates is valuable. It omits invalid-postcode behavior but is otherwise sufficiently complete.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.