A persistent identifier for the merge field, which remains the same even if the field's settings are modified.

The merge tag used to reference this field in Mailchimp campaigns, templates, and the /members endpoint.

The data type of the merge field, such as text, number, date, address, or phone.

Indicates whether the merge field must be filled in by subscribers when joining the list.

The default value assigned to the merge field if no value is provided by the subscriber.

Specifies whether the merge field is visible to subscribers on signup forms.

Determines the order in which the merge field appears on signup forms, with lower numbers appearing first.

In address fields, defines the default country code to use if the subscriber does not specify one.

In phone number fields, defines the expected format (for example, 'US' or 'International').

In date or birthday fields, specifies the format used to display and capture dates.

For radio buttons or dropdown lists, lists the available options that subscribers can choose from.

In text fields, defines the default length or character limit for the field input.

Optional help text displayed to guide subscribers when filling in the field.

The unique identifier of the Mailchimp list that this merge field belongs to.