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: "7fa0b13ea4ae26c462be8896d1a11e72384b07ec0b2309ec37261bac206966a9"
Vary: Accept

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