Sample API.AI emojis entity export in JSON format. On importing this JSON into another agent, it creates an entity names @emoji and will have values and can detect emoji's like 'smile', 'like', etc. This is not a comprehensive list, just an example.

emoji.json

{
  "id": "bff8ea0a-b4ff-4ea8-8691-ca22f05187e9",
  "name": "emoji",
  "isOverridable": true,
  "entries": [
    {
      "value": "smile",
      "synonyms": [
        "\"☺\"",
        "\":smile:\"",
        "😀",
        "😃",
        "😄",
        "😁"
      ]
    },
    {
      "value": "like",
      "synonyms": [
        "\":thumbsup:\"",
        "\"(y)\"",
        "👍",
        "👌"
      ]
    },
    {
      "value": "sad",
      "synonyms": [
        "\"☹\"",
        "\":disappointed:\"",
        "😔",
        "😞",
        "😟",
        "😕",
        "🙁"
      ]
    },
    {
      "value": "kiss",
      "synonyms": [
        "\"😗\"",
        "\":kissing_heart:\"",
        "\":heart_eyes:\"",
        "😘",
        "😍",
        "😗",
        "😙",
        "😚"
      ]
    },
    {
      "value": "tease",
      "synonyms": [
        "\":P\"",
        "😋",
        "😜",
        "😝",
        "😛",
        "\":stuck_out_tongue_winking_eye:\"",
        "\":stuck_out_tongue_closed_eyes:\"",
        "\":stuck_out_tongue:\""
      ]
    }
  ],
  "isEnum": false,
  "automatedExpansion": true
}