How can I correctly create a script tag with JavaScript?

[cerz01]

I'm trying to create a tag script using the documentation: https://shopify.dev/docs/api/admin-rest/2023-10/resources/scripttag#post-script-tags
But when I try to use the code provided I am told that shopify is not defined, and furthermore shopify does not have a rest attribute, where am I wrong?
I need to customize the app within the app section, and then create and upload the component to the shopify store, I also looked for a way to pass the parameters between the app._index.jsx file to the liquid file which deals with the creation of the HTML tag code to be loaded into the store (obviously in vain given the different type of compilation). I'm also open to new solutions, thanks in advance