For non-programmatic usage and verification, the extensions can be easier?
On a similar topic HIBP allowed people to request versioning via a custom HTTP Header, a Accept Content-Type, or a version segment in the URL path and approximately everyone went with option 3.
"For non-programmatic usage and verification," it should be served in a human-readable manner, typically including things like formatting, and maybe even syntax coloring if you're feeling nice.
Take my `Accept: text/html` and give me my HTML-ified JSON, dangit! ;)
I've actually seen APIs with "pretty=true" or "indent=4" type query parameters to emit formatted JSON for people before, though it doesn't go as far as HTML with syntax colouring.
This has always disturbed me, considering that HTTP has had content negotiation for ... oh, basically its entire history [https://www.w3.org/Protocols/HTTP/1.0/spec.html#Accept].