Watson: Quick Replies within Slots JSON

Question

I'm trying to insert Facebook quick replies within a Watson dialog slot. I managed to do it at the node level, but cannot do it at the slot level. The syntax I'm using is this - same as the one at the node level, except I'm specifying the context variable @stress_q1:

{
  "context": {
    "stress_q1": "@stress_q1"
  },
  "output": {
    "text": {
      "values": [
        "Q1: I've been feeling optimistic about the future."
      ],
      "selection_policy": "sequential"
    },
    "context": {
      "facebook": {
        "text": "I've been feeling optimistic about the future.",
        "quick_replies": [
          {
            "title": "None of the time",
            "payload": "None of the time",
            "content_type": "text"
          },
          {
            "title": "Rarely",
            "payload": "Rarely",
            "content_type": "text"
          },
          {
            "title": "Some of the Time",
            "payload": "Some of the Time",
            "content_type": "text"
          },
          {
            "title": "Rarely",
            "payload": "Rarely",
            "content_type": "text"
          },
          {
            "title": "All of the time",
            "payload": "All of the time",
            "content_type": "text"
          }
        ]
      }
    }
  }
}