MPA-LOCK (BUYER)

{
  "version":"0.0.1.0",
  "mpaction": [
    {
      "action": "MPA_LOCK",
      "listing": "listings_hash" 
      "nonce": "randomness",
      "info": {
        "address": "20 seventeen street, march city, 2017",
        "memo": "Please deliver by 17 March 2017"
      },
      "escrow": {
        "rawtx": "...."
      }
    }
  ]
}

MPA-LOCK (SELLER)

{
  "version":"0.0.1.0",
  "mpaction": [
    {
      "action": "MPA_LOCK",
      "listing": "listings_hash" 
      "nonce": "randomness",
      "info": {
        "memo": "Will deliver by then, setting lockup lower, no more negotiations..."
      },
      "escrow": {
        "rawtx": "...."
      }
    }
  ]
}