Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a parameterless read tool, the description is mostly sufficient: an agent knows what it returns and the visibility caveat. However, with no output schema and no annotations, the agent is left guessing about the response shape (e.g., per-course objects, numeric scores, letter grades), which is a meaningful gap for a tool whose entire purpose is returning data.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.