Using this json, I have updated schema to include "fist" name and "last" name.

{
  "csrf_token": "",
  "method": "password",
  "password": "P@ssw0rd123",
  "traits": {
    "email": "<mailto:john@abc.com|john@abc.com>",
    "first": "john",
    "last": "doe"
  }
}