When enabled, the build will be rejected if the user submits an empty value for this parameter. This enforcement applies at the server side, so it covers the Build with Parameters form, Rebuild, the REST API, and the CLI.

This option is most useful for Check Boxes, Multi Select, and Radio Buttons choice types, where the user can submit the form without selecting any option. For Single Select parameters a value is always included in the submission when the choices list is non-empty, so the flag has no practical effect there.

The browser-side validation (inline error message and disabled Build button) provides early feedback, but server-side enforcement is the authoritative gate.