Are the URLs in your data arbitrary URLs, or do they represent relations among the resources & collections presented by your application?
If the former, they should just be attributes.
If the later, they should be presented using the corresponding properties in
links objects. If they don’t correspond to the specific uses described in the specification, they should be considered arbitrary, and should not be added to
links are sufficiently anemic that it’s unlikely to be relevant outside the specific JSON:API usages described in the specification. I understand that’s going to be expanded in 1.1, but the defined link relations registered with IANA aren’t that interesting (mostly because each is too vague).
Or at least that’s my understanding from reading the specification.