[exogen]

The schema should still be documented somewhere, like any API. But even if it's not: GraphQL supports a special "introspection query" that will tell you the entire schema that you can query. Pointing a tool like GraphiQL (https://github.com/graphql/graphiql) at a GraphQL endpoint will even run the introspection query automatically and turn the result into rendered explorable documentation. That's how you figure out what to query.