Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations provided, the description carries the burden of behavioral disclosure. It discloses that the optimization is lossless, uses oxipng for PNG, re-encodes JPEG at high quality, and has a free tier limit. However, it does not describe the response format, file size limits, or error behavior, leaving some behavioral aspects ambiguous.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.