Available parameters and response documentation is available here

GET /lookup/chr17:7578443:A:T?format=api
HTTP 200 OK
Allow: GET, HEAD, OPTIONS
Content-Type: application/json ;utf-8
ETag: "9b24e0394133284b740dc773e50297fa56ff52abb183d3c6af71dead1dc7444b"
Vary: Accept

{
  "chromosome": "chr17",
  "alt": "T",
  "ref": "A",
  "pos": 7578443,
  "variant_id": "10190170075784430004",
  "variant_type": "SNV",
  "cytobands": "17p13.1",
  "publication_counts": null
}