Back when looking into JSON Feeds it didn’t link to its schema, but there’s one in SchemaStore/schemastore and sonicdoe/jsonfeed. You could validate a feed with a tool like check-jsonschema.
$ check-jsonschema --schemafile jsonfeed-v1.1.json feed.json ok -- validation done
The upside of the Feed is a lot more human than technical in the sense that it’s a mapping of /Atom to the world. There are many people who prefer JSON over .