Either a token, like the ones returned by [Stripe.js](https://stripe.com/docs/js), or a dictionary containing a user's bank account details.

When set to true, or if this is the first external account added in this currency, this account becomes the default external account for its currency.

Specifies which fields in the response should be expanded.

A token, like the ones returned by [Stripe.js](https://docs.stripe.com/js) or a dictionary containing a user's external account details (with the options shown below). Please refer to full [documentation](https://stripe.com/docs/api/external_accounts) instead.

Set of [key-value pairs](https://docs.stripe.com/api/metadata) that you can attach to an object. This can be useful for storing additional information about the object in a structured format. Individual keys can be unset by posting an empty value to them. All keys can be unset by posting an empty value to `metadata`.