Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The readOnlyHint annotation already signals a non-destructive operation. The description adds detail about what the tool returns (word, character, sentence, paragraph stats), giving the agent a clear behavioral expectation. It does not dive into tokenization edge cases or the exact meaning of 'paragraph statistics,' but for a tool of this simplicity, the added context is valuable.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.