To create a new user account, provide the information you have in the POST request along with the redirect URLs for success and failure. Then present the user with the onboarding_url by either redirecting (browser) or opening an In-App browser.

Once complete, the browser will redirect to one of your specified callbacks. If necessary, close the In-App browser and report the result to the user.

This will create a user account that can only accept payments. The user now has to transfer money to that account's brokerage_bank_account to complete the onboarding process.

Take a look at this sequence diagram for a visualization:

sequence diagram of account creation flow

Click Try It! to start a request and see the response here!