Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations at all, the description carries the full burden and does disclose the concrete return payload (DESIGN.md content, preview_html, tokens, URL), which is real behavioral value since no output schema exists. It says nothing, however, about auth requirements, what happens if neither id nor slug resolves, or error behavior on an unknown system.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.