Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden. It explicitly states the return content (abstract, authors, date, volume/issue, MeSH headings), making the behavior transparent. It does not disclose error handling or rate limits, but these are not critical for a simple read-by-ID operation.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.