Available parameters and response documentation is available here

GET /lookup/TP53:R175L?format=api
HTTP 200 OK
Allow: GET, HEAD, OPTIONS
Content-Type: application/json ;utf-8
ETag: "883530e9b08d9ad67a1b5e08c09c775cb5a8ff4e93b2b5c8a65f298f723a11f0"
Vary: Accept

{
  "chromosome": "chr17",
  "alt": "A",
  "ref": "C",
  "pos": 7578406,
  "variant_id": "10190170075784060001",
  "variant_type": "SNV",
  "cytobands": "17p13.1",
  "publication_counts": null
}