Swagger is the most widely used tooling ecosystem for developing APIs with the OpenAPI Specification(OAS).
The Estuary API Swagger to document and extend it's APIs.
Swagger has a great interface that allows developers to test out the endpoints without having to download and run the node.
You can view the quick guide on how to get an API key here
Open the Estuary API Swagger UI here
Once you have the API key, you would need to put this key on the Authorized modal popup.
Go here to test out a few examples.