Live API does not show alternative content type

When I use the Live API with my endpoints it always shows this:

I'm guessing that since I use content-type `application/vnd.api+json` in my response, that this is not picked up.

Is there any way to tell the Live API to accept a different content type?

Start by reproducing the Live API behavior with an endpoint returning application/vnd.api+json, then trace how the Live API determines accepted response content types. Confirm how the documented or displayed content type is selected; done means an alternative content type is recognized and shown correctly.

Written by the indexing model from the issue text.