Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden. It does disclose two useful behavioral facts: only public posts are readable (so drafts/private content is out of scope) and the response includes the Markdown body. It says nothing about behavior on missing/private posts, authentication requirements, or rate limits.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.