{
  "kind": "capability_negotiation",
  "expect": "valid",
  "description": "unsupported with explicit failure_class=payload_too_large -> do_not_retry",
  "data": {
    "outcome": "unsupported",
    "explicit_failure_class": "payload_too_large",
    "expected": {
      "failure_class": "payload_too_large",
      "retry_class": "do_not_retry"
    }
  }
}
