Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries full responsibility for behavioral disclosure. It does mention that the return value is a 'フォーマットされた文字列' (formatted string), which is helpful. However, it does not disclose potential errors, units, or any other behavioral nuances. For a simple read operation, this is adequate but minimal.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.