Available parameters and response documentation is available here

GET /lookup/KRAS:G12D?format=api
HTTP 200 OK
Allow: GET, HEAD, OPTIONS
Content-Type: application/json ;utf-8
ETag: "9ee63b5b9f632633503e8812feb0d2ce97ae7b307bf506112bde422576b36f78"
Vary: Accept

{
  "chromosome": "chr12",
  "alt": "T",
  "ref": "C",
  "pos": 25398284,
  "variant_id": "10190120253982840004",
  "variant_type": "SNV",
  "cytobands": "12p12.1",
  "publication_counts": null
}