The entire GraphQL schema is available to fetch from the API itself. It's called introspection.
As with every other query, introspection of the Ergonode API requires authentication.
The simplest way to discover the GraphQL API is to use supporting HTTP clients like Insomnia. On one hand, they do support scoping through documentation schema, and on the other provide autocomplete functionality which makes writing queries really straightforward.
Alternatively, in order to obtain the full types definition download the schema