Using this add-on, you can define tags to add to the host page by adding annotation to your UI class. Annotations are provided for generic and tags as well as a specific annotation for adding a viewport meta tag. The structure is extensible to allow you to define your own tags and annotations if necessary. As an example, you can write something like this: @Viewport("width=device-width, initial-scale=1") @Link(rel = "example", href = "about:blank") public class MyUI extends UI { ... }