Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a one-parameter read-only tool with full schema coverage, rich annotations, and an output schema, the description supplies the important context: data source, network-wide scope, no sender filter, return contents, and cost/auth model. An agent has enough to invoke it correctly.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.