Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a simple read-only tool with one parameter and an output schema (present but not shown), the description explains the data origin (validation scan), notes it's free, and summarizes output (scheme names and fit). This, combined with annotations and schema, provides complete guidance.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.