Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a single-parameter read tool with an output schema and comprehensive annotations, the description covers source, authentication, return-field expectations, and how to obtain the id. Nothing needed for correct invocation is missing; the minor sibling-name typo is the only blemish.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.