Available parameters and response documentation is available here

GET /lookup/BRAF:V600E?format=api
HTTP 200 OK
Allow: GET, HEAD, OPTIONS
Content-Type: application/json ;utf-8
ETag: "0984558fd80253c7a9403dd83c0484e6eb35ddf249e1cb3eafb48b6753f779ce"
Vary: Accept

{
  "chromosome": "chr7",
  "alt": "T",
  "ref": "A",
  "pos": 140453136,
  "variant_id": "10190071404531360004",
  "variant_type": "SNV",
  "cytobands": "7q34",
  "publication_counts": null
}