Like

?itemtype=Member
&field=name
&match=natko

Response (123 bytes)

[
    {
        "id": 37,
        "name": "natko"
    },
    {
        "id": 1385156,
        "name": "NatkosClone"
    }
]

This help response is displayed by adding &help to any API call. Use the Raw Response in your apps.