Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations provided, the description carries the full behavioral burden, and it does disclose meaningful behavior: it returns null when no separate config file exists. This is genuinely useful for an agent deciding whether the config is present. It doesn't mention side effects, but for a get operation the main ambiguity (the null case) is covered.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.