Can you only use directives with

Boolean!

variables? Can’t you check if a

String!

is empty or not or do I have to to it like this? ->

query ($offerId: String!, $offerIdExists: Boolean!) {
    offer(offerId: $offerId) @include(if: $offerIdExists) {
      id
    }
  }

Yes, those directives only work with booleans...