Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the tool has 0 parameters, 100% schema coverage, and an output schema exists, the description's job is reduced. However, it's a backup operation with no annotations, and the description doesn't explain what 'backup' entails (e.g., file format, location, or if it's a destructive read). With output schema handling return values, the description is minimally adequate but lacks context for a mutation-like tool.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.