After getting rates, you can purchase an available shipping service. If additional inputs are required for the service you want to purchase, you must provide them when you call this purchaseShipment operation as part of this step.
You must complete the purchase with the response provided from the get rates API. If you make the request after requestToken have expired, you will receive an error response with the error code of TOKEN_EXPIRED. If you receive this error response, you must execute the rate request for the shipment again.