Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations provided, the description carries the full burden of behavioral disclosure. 'Update' implies mutation, and 'existing' indicates the target must already exist, but nothing is said about side effects, whether this is a partial or full replacement, permissions, or idempotency. This is insufficient for a mutation tool.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.