AWS CodeStar SNS notification delivers JSON as email body

I have created a notification rule in CodeBuild to deliver notifications about build errors by e-mail. Unfortunately, the generated emails are just a plaintext email with the body being a truckload of JSON and not, like e.g. Cloudwatch Alerts, a proper human-readable text. What am I doing wrong?

I created the rule and SNS topic using this Terraform code:

resource "aws_sns_topic" "build-monitoring" {
  name              = "build-monitoring"
}

resource "aws_codestarnotifications_notification_rule" "build-monitoring" {
  name        = "build-monitoring"
  detail_type = "BASIC"
  event_type_ids = [
    "codebuild-project-build-state-failed",
    "codebuild-project-build-state-succeeded",
    "codebuild-project-build-state-stopped",
  ]
  resource = aws_codebuild_project.project.arn
  target {
    type    = "SNS"
    address = aws_sns_topic.build-monitoring.arn
  }
}