maputnik/src/config/tilesets.json

{
  "mapbox-streets": {
    "type": "vector",
    "url": "mapbox://mapbox.mapbox-streets-v7",
    "title": "Mapbox Streets"
  },
  "openmaptiles": {
    "type": "vector",
    "url": "https://free.tilehosting.com/data/v3.json?key=25ItXg7aI5wurYDtttD",
    "title": "OpenMapTiles"
  },
  "tilezen": {
    "type": "vector",
    "tiles": [
      "http://tile.mapzen.com/mapzen/vector/v1/{layers}/{z}/{x}/{y}.pbf?api_key=mapzen-RVcyVL7"
    ],
    "minZoom": 0,
    "maxZoom": 15,
    "title": "Mapzen Vector Tile Service"
  }
}