Every API has the following properties shown on the API page on the website.
Shows the availability of your API to the public and has one of a few values:
The secret key used to authenticate your API to PayPIs servers.
This secret provides the ability to charge customers of your API, store this securely.
Used to make test requests to your API for free. Requests are still shown in usage information but earnings are not made available to you (for quite obvious reasons).
This secret allows unrestricted requests to your API without paying, keep it safe.
A URL you can redirect clients to so they can subscribe to your API
This is the main way to get users to subscribe to your API. Share this with your users where you document and describe your API.