Comment by nivertech

I'd rather pay with with utility isEvenCoins, rather than with USD.

Also, our entire stack is GraphQL-based, so we must have a GraphQL API according to this schema:

    schema {
      query: Query
      mutation: Mutation
      subscription: Subscription
    }
    
    type Query {
      balance: Int!
      isEven(input: isEvenInput!): isEvenPayload!  
    }
    
    type Mutation {
      depositCoins(amount: Int!): DepositPayload!  
      withdrawCoins(amount: Int!): WithdrawPayload!
    }
    
    type Subscription {
      coinsDeposited: Int!
      coinsWithdrawn: Int!
      coinsSpent: Int!
    }
    
    input isEvenInput {
      number: Int!
      gas: Int!
    }
    
    type isEvenPayload {
      result: bool
      balanceLeft: Int!
      isError: bool!
      errMsg: String
    }
    
    type DepositPayload {
      newBalance: Int!
      isError: bool!
      errMsg: String
    }
    
    type WithdrawPayload {
      newBalance: Int!
      isError: bool!
      errMsg: String
    }