Create or update split 1 or split 2 of a worker's direct deposit. If the bank account split exists it's updated in place, otherwise it's created. Bank account splits must be created in order, so split 2 requires split 1.
Send the full accountNumber when creating a bank account split. When updating, omit it to keep the stored account number. percentPerPayment is a whole number from 1 to 100.
Don't send a bank name. Everee determines it from routingNumber, which must be a routing number in the Federal Reserve directory. In a sandbox company you can use reserved test routing numbers to get a predictable result. See the Guide to the Worker Direct Deposit API for details, including the sections on routing numbers and bank names and testing in the sandbox.