Servers can return something like: Link: </foo>; rel="alternate" type="application/json" You could return multiple of these as a response to a HEAD reques

Servers can return something like: Link: </foo>; rel="alternate" type="application/json" You could return multiple of these as a response to a HEAD request for example. You could also use the Accept header in response to a HTTP OPTIONS request, or as part of a 415 error response. Accept: application/json, text/html https://httpwg.org/specs/rfc9110.html#field.accept https://httpwg.org/specs/rfc9110.html#field.accept (yes Accept can be used in responses) .well-known is not a good place for this kind of thing. That discovery mechanism should only be used in situations where only a domainname is known, and a feature or endpoint needs to be discovered for a full domain. In most cases you want a link. The building blocks for most of this stuff is certainly there. There's a lot of wheels being reinvented all the time.