Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The annotations already declare readOnlyHint=true and openWorldHint=true, indicating a safe read operation. The description, though brief, adds valuable context by specifying the required format of the encrypted user ID (29-bit lowercase hex). However, it doesn't disclose potential failure cases or error behavior, but given the annotations, the bar is lowered and this additional format detail justifies a 4.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.