Available parameters and response documentation is available here

GET /lookup/15-73027478-T-C?format=api
HTTP 200 OK
Allow: GET, HEAD, OPTIONS
Content-Type: application/json ;utf-8
ETag: "8b44ce74d0e7ecbf212acc58e2b35b214e27486b9f05d84109dcdf65121b5a84"
Vary: Accept

{
  "chromosome": "chr15",
  "alt": "C",
  "ref": "T",
  "pos": 73027478,
  "variant_id": "10190150730274780002",
  "variant_type": "SNV",
  "cytobands": "15q24.1",
  "publication_counts": null
}