GraphQL Schema Building - Suggestion for good Book, Article, or Software

I have set up a new GraphQL API using Realm

I am having difficulty however figuring out the correct syntax to create a Schema to specify my queries - the built-in schem creation capability of Realm appears to create only a very basic schema

Can anyone suggest schema-creation software for MongoDb or a good book or article or youtube which explains well how to set up a schema?

I tried using this site GraphQL schema basics - Apollo Server - Apollo GraphQL Docs as a reference, but when I try its examples to define an object type in a schema it is rejected by the Realm schema editor as “Invalid JSON.”