Create your own component that consumes the content fragment. use the Granite UI, pathfield, to point to your content fragment, then using backend logic to expose properties to slightly via Sling Models.
API: When you want to expose Json to 3rd party services, you can utilise the WCM Core Component V2 Page, and also the WCM Core Component content fragment component, you can call model.json on the page, and see the basic structure of the content fragment values presented as the JSON response.