In your credentials json file you must provide your NS1 api key:
{
"ns1":{
"api_token": "your-ns1-token"
}
}
This provider does not recognize any special metadata fields unique to NS1.
Example Javascript:
var REG_NONE = NewRegistrar('none', 'NONE')
var NS1 = NewDnsProvider("ns1", "NS1");
D("example.tld", REG_NONE, DnsProvider(NS1),
A("test","1.2.3.4")
);