The purpose of a discovery endpoint is so that a human being and a machine should be able to discover information and documentation about the data product from the data product itself.
For human beings, the discovery endpoint needs to make the documentation and metadata available in HTML format. For machines, the documentation and metadata should be obtainable from the discovery endpoint in JSON format
The /docs webpage also allows a developer to test the REST API endpoints by authenticating and passing in query parameters
The GraphQL standard allows a developer to access information about the GraphQL API from the /graphql endpoint