Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description must carry behavioral weight; it discloses that the operation is offline and read/compute-oriented (word counting), which suggests no mutation. It does not, however, describe output structure, error behavior, or file expectations beyond calling the file 'saved notes'.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.