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: "ca686fffb3387ae1f58d22ee8fd3b3aea3368b5500beb75cf8e153663c13fe24"
Vary: Accept

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