How to approach a GraphQL query that returns a boolean value?

Question

Need to check whether an email is available or taken during the user sign-up process. The goal is to quickly query, using GraphQL, the API server and have it tell us if the email is available or taken.

What is the general best practice on a simple boolean-ish type of situation using GraphQL?

Below is what I have come up with but I am unsure if this is a good practice or not and want to hear feedback on a better practice on queries like this.

Request:

query {
  emailExists(email:"[email protected]") {
    is
  }
}

Response:

{
  "data": {
    "emailExists": {
      "is": true
    }
  }
}

Answer 1

A "query" is just a field on what happens to be the Query type. A field can return any output type, including scalars -- it doesn't need to return an object. So it's sufficient to have a schema like:

type Query {
  emailExists(email: String!): Boolean!
}

The only reason to prefer an object type would be if you anticipated wanting to add additional fields in the future (i.e. something other than your current is field).