GraphQL Custom Input Type

I’d like to use a mutation that requires a custom input type. When I try this I get an error. See below:

    input AdminApplicationUpdateInput {
          tastingReceivedAt: DateTime
          tastingResult: String
          tastingResultReceivedAt: DateTime
          onboardingCallCompletedAt: DateTime
          archiveReason: String
          adminNotes: String

    mutation UpdateApplicant ($userId: String!, $input: AdminApplicationUpdateInput!) {
      adminUpdateApplication(userId: $userId, input: $input)

[{“message”:“The AdminApplicationUpdateInput definition is not executable.”,“status”:415}]