Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a simple tool with one parameter fully described in the schema, annotations for read-only, and an output schema absent but with return value disclosed in the description, the definition is nearly complete. It covers what, when, cost, and return format. Missing details like error handling or image quality requirements are minor given low complexity.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.