Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations supplied, the description carries the full burden. It does disclose a meaningful side effect — the opened document becomes the active document — which is real behavioral context an agent needs. It says nothing about what happens to any already-open document, whether the file is locked or read-only, or what errors occur on a bad path, so it is only partially transparent for a state-changing operation.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.