Is there any API which add custom shipping rates in order which is order by customers. I want API to achieve this task. It is really great if I can add custom shipping rates with fulfilment order API. Please note: amount is unpredicted cannot base on any calculator. Amount is base on third party as they charge for shipping.
You might like to checkout our Carrier Service API(documentation here) which would serve applicable shipping rates to customers at checkout. Please let me know if you have any further questions.