How do you add a comment to a json IAM policy?

Question

IAM policy are complicated beasts. It would be nice to add a comment when crafting them. For example,

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "Stmt1422979261000",
      "Effect": "Allow",
      "Action": [
        "route53:ListHostedZones",
      ],
      "Comment": "Foo"
      # or Bar
      "Resource": [
        "*"
      ]
    }
  ]
}

Neither of these work. Does there exist a way to add comments to these policies?

Answer 1

Hyper Anthony's answer is correct in the strict sense of 'comment' - however, in most situations you can at least use the Sid for pseudo comments to communicate the intent or any constraints etc.:

The Sid (statement ID) is an optional identifier that you provide for the policy statement. You can assign a Sid value to each statement in a statement array. In services that let you specify an ID element, such as SQS and SNS, the Sid value is just a sub-ID of the policy document's ID. In IAM, the Sid value must be unique within a policy. [emphasis mine]

This is e.g. exemplified by the use of TheseActionsSupportResourceLevelPermissions within the (very helpful) AWS blog post Demystifying EC2 Resource-Level Permissions:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "TheseActionsSupportResourceLevelPermissions",
            "Effect": "Allow",
            "Action": [
                "ec2:RunInstances",
                "ec2:TerminateInstances",
                "ec2:StopInstances",
                "ec2:StartInstances"
            ],
            "Resource": "arn:aws:ec2:us-east-1:accountid:instance/*"
        }
    ]
}

• As mentioned in Sid some services might require this element and have uniqueness requirements for it, but I haven't experienced resulting naming constraints yet.