As of v2022.12 [PiHole requires the use of an API key](https://pi-hole.net/blog/2022/11/17/upcoming-changes-authentication-for-more-api-endpoints-required/#page-content) if an admin password is set. Older versions do not require any authentication even if the admin uses a password.
Note: by default the "blocked" and "blocked_percent" fields are merged e.g. "1,234 (15%)" but explicitly including the "blocked_percent" field will change them to display separately.