Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations provided, the description carries the full behavioral burden. 'Get a list of all available' implies a read-only, complete retrieval with no filtering or side effects, which is useful context. However, it does not clarify whether the list is static, project-dependent, or returned in any particular format.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.