Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations provided, the description carries the full burden, and it discloses the key behavioral traits: no payment required, a 30 req/min rate limit, and identical data to the paid sibling. It does not describe the exact output shape, but the return content (prices for five assets) is implied clearly enough.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.