Available parameters and response documentation is available here

GET /lookup/chr11-117222650-A-?format=api
HTTP 200 OK
Allow: GET, HEAD, OPTIONS
Content-Type: application/json ;utf-8
ETag: "91d85e0fd1a2a43a6b9616a3167946480b9232f48cdb9f66e1730afa2595cdf7"
Vary: Accept

{
  "chromosome": "chr11",
  "alt": "",
  "ref": "A",
  "pos": 117222650,
  "variant_id": "10190111172226509001",
  "variant_type": "Deletion (homopolymer)",
  "cytobands": "11q23.3",
  "publication_counts": null
}