Which web markup is required for Apple to add a page to the Public Spotlight Index?

I'd like to publicly index pages on my website that also exist within my app, so that, when installed, users can see app content in Spotlight Search on iOS9 and above.

However, I'm finding the Mark Up Web Content documentation confusing and contradictory.

For example, it states:

Although you must supply the deep link, title, and description elements to index an item, it’s strongly recommended that you also include a content-specific image.

But, having implemented Universal Links, as recommended by Apple, there is no Deep Link to specify, so I shouldn't need 'Smart App Banners', 'Twitter Cards' or 'Facebook App Links', and I can't see how else a deep link could be specified here.

Also, given all pages have Title and Description metadata tags, is it still necessary to specify the same again in Schema or Open Graph?

Thanks for your help