Post a json api having dynamic values to an external domain.

Hi,

I have created a custom REST resource(using a custom module) for posting product details in my drupal site to an external site.
The products ae actually displayed as blocks each having a 'buy now' button. My requirement is when someone clicks the 'buy now' button, the REST resource I created needs to be updated with the details of the product(eg: product name, id, description, price etc) selected and then redirect the user to the external site with all these product details.

Is this achievable? Can a rest resource be updated with dynamic data based on a button click?
Would really appreciate if anyone can help me on this.