Cardano NFT format
{
  "721": {
    "{policy_id}": {
      "{policy_name}": {
        "name": "<required>",
        "description": "<optional>",
        "sha256": "<required>",
        "type": "<required>",
        "image": "<required>",
        "location": {
          "ipfs": "<required>",
          "https": "<optional>",
          "arweave": "<optional>"
        }
      }
    }
  }
}

Steam item format
{
  "itemdefid": 10,
  "type": "playtimegenerator",
  "bundle": "100x100;101x50;102x25;103x2;110x20;111x20;120x5;121x3",
  "name": "Drop Generator",
  "name_color": "7D6D00",
  "background_color": "3C352E",
  "item_slot": "generator",
  "icon_url": "http://cdn.beta.steampowered.com/apps/440/icons/c_fireaxe_pyro_xmas_large.fa878752e1aa09a721a03042a234063b6c929278.png",
  "icon_url_large": "http://cdn.beta.steampowered.com/apps/440/icons/c_fireaxe_pyro_xmas_large.fa878752e1aa09a721a03042a234063b6c929278.png",
  "tradable": false,
  "marketable": false
}