| string | field_type | optional - one of: text, number, radio, dropdown, date, address, phone, url, imageurl, zip, birthday - defaults to text |
| boolean | req | optional - indicates whether the field is required - defaults to false |
| boolean | public | optional - indicates whether the field is displayed in public - defaults to true |
| boolean | show | optional - indicates whether the field is displayed in the app's list member view - defaults to true |
| string | default_value | optional - the default value for the field. See listSubscribe() for formatting info. Defaults to blank |
| array | choices | optional - kind of - an array of strings to use as the choices for radio and dropdown type fields |
| string | dateformat | optional - only valid for birthday and date fields. For birthday type, must be "MM/DD" (default) or "DD/MM". For date type, must be "MM/DD/YYYY" (default) or "DD/MM/YYYY". Any other values will be converted to the default. |
| string | phoneformat | optional - "US" is the default - any other value will cause them to be unformatted (international) |
| string | defaultcountry | optional - the ISO 3166 2 digit character code for the default country. Defaults to "US". Anything unrecognized will be converted to the default. |