Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden. It discloses that the operation is a read and that the return value is a string, which implies non-mutation and gives the result type. However, it does not address error cases, file encoding, path resolution, or binary file behavior.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.