Exploring the Schema

query IntrospectionQuery {
  __schema {
    queryType {
      name
    }
    types {
      name
      kind
      description
      fields {
        name
        description
        type {
          name
          kind
        }
      }
    }
  }
}

{
  "data": {
    "__schema": {
      "queryType": {
        "name": "Query"
      },
      "types": [
        {
          "name": "HelloInput",
          "kind": "INPUT_OBJECT",
          "description": null,
          "fields": null
        },
        {
          "name": "String",
          "kind": "SCALAR",
          "description": "The `String` scalar type represents textual data, represented as UTF-8 character sequences. The String type is most often used by GraphQL to represent free-form human-readable text.",
          "fields": null
        }
      ]
    }
  }
}