Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=false, destructiveHint=false, and openWorldHint=true, so the agent knows this performs a non-destructive but state-changing, network-touching operation. The description adds the scope of what is fetched (dependencies + type definitions), which is useful given the ambiguous "download" framing. It does not disclose where artifacts land, whether existing files are overwritten, or auth/network requirements beyond the annotation.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.