The Platform API for Partners provides many official endpoints that the App Info API doesn’t support. These endpoints let you introspect security settings, discover other customer instances of the same add-on, and much more. Platform API for Partners endpoints are also more consistent and “better traveled.” Heroku uses these endpoints internally, and customers also use them directly.
With the Platform API, add-ons have an OAuth client secret and a number of OAuth authorizations, one token per provisioned add-on. The OAuth client secret is only used to authenticate requests to create the scoped tokens; it is not used to authenticate other requests to the Platform API.
All new add-ons that require Platform API functionality should access it via the Platform API for Partners. If you have an existing add-on that accesses Platform API endpoints via a different method, it’s recommended that you update your add-on to use the Platform API for Partners instead.
Learn more in the Platform API for Partners announcement and check out the Platform API for Partners documentation for details on how resources returned from the API are scoped.