webscraping – request with dynamically generated parameter

One thing I’ve alawys wanted was to write an auto checkout bot/monitoring bot for more complex websites. The problem I encountered is as follows:

There is some ‘hidden’ data on the website I’m trying to scrape, which contains stuff such as product stock etc.

It’s all in a response of a request, which looks like this:
https://site-api.site_name.com/shop/v1/shop/productDetails?spuId={spuId}&s={sValue}&t={tValue}

I know that t is just a timestamp, but value s, is dynamically generated (I assume so, because it changes everytime I refresh the website).

I also noticed that in this api headers is a “X-sign” header, which contains some value and a timestamp. (I don’t know if it could be anyway useful)
enter image description here

How do I find out how is “s” generated? I’m sure it’s possible.