Available parameters and response documentation is available here

GET /lookup/TP53:R273H
HTTP 200 OK
Allow: GET, HEAD, OPTIONS
Content-Type: application/json ;utf-8
ETag: "31ae8e800a7cde277061f0ca356528f0b6700a00"
Vary: Accept

{
  "chromosome": "chr17",
  "alt": "T",
  "ref": "C",
  "pos": 7577120,
  "variant_id": "10190170075771200004",
  "variant_type": "SNV",
  "cytobands": "17p13.1-17p13.1",
  "publications": {
    "publications": [],
    "genes": []
  }
}