How to create a smart button similar to Paypal or Amazon to integrate with my application

I'm creating a shipping application using react as the front end and node.js as the back end. The application provides shipping services for users who wants to ship their items from one location to other location.

I'm planning to enable my application to be integrated with other applications such as e-commerce apps so that whenever the customers of the e-commerce apps wants to ship the purchased items to somewhere, they could choose services provided by my application directly from the ecommerce apps without leaving the e-commerce apps.

I was just thinking of two alternatives to do that, first by creating API in my node.js app so that the e-commerce apps just need to call the API with the parameters required. But, I think this would be too complicated for the e-commerce developers as they needs to send a lot of parameters that needs to be fitted with my requirement

Second alternative is that I could create a smart button in javascript like that of Paypal or Amazon so the developers of the e-commerce apps just need to put the button script to their apps, and when the customers hit the button, the page will be redirected (along with just few parameters--instead of many parameters as of that required by the first alternative --such as items that the customers want to ship) to my page. Then, my page will do the rest of the logic

I wonder how to do the second alternative as I still don't have any reference/example to do that

Thanks