Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a zero-parameter tool with no output schema, the description covers the key aspects: purpose, payment, error behavior, and authentication. The reference to the instruments tool for parameter details is a sensible pointer. It doesn't describe what the successful output looks like, but given the absent output schema and simplicity, this is acceptable. It's mildly incomplete because it doesn't hint at the response format, but for a paid pick service it adequately sets expectations.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.