Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden of behavioral disclosure. It only states the basic operation 'Get environment variables' and does not disclose return format, failure modes, or whether it returns all variables when none specified (though the schema covers that). It implies a read-only operation via 'get', but lacks richer context.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.