Can't make delete mutation work

On the graphql playground, I’m not able to run the following delete mutation:

mutation deleteLyric($id: ID!){
  lyrics {
    deleteLyric(id:$id) {
      data
      error {
        message
        code
        data
      }
    }
  }
}

The result says:

{
  "data": {
    "lyrics": {
      "deleteLyric": {
        "data": null,
        "error": {
          "message": "Validation failed.",
          "code": "VALIDATION_FAILED_INVALID_FIELDS",
          "data": null
        }
      }
    }
  }
}

I’m not sure what kind of validation is failing… :thinking: Is there anyone else who encountered a similar thing?