I am creating a dynamic link by passing the fields st, sd and si now user has copied that link and pasting in the chat field on my website and I want to implement unfurling logic like slack and show the preview.

When I try to get the meta tags of the link(shortened) I get the meta tags of page to which i will be redirected.
But I want to show the data which i passed to st, sd and si while creating the link.

So how to do it?
Somehow slack and other chat platforms are able to get it but I am not getting that tag anywhere.

So where and how can I get that data.

Here is the example how slack shows the preview

and here is what meta tags I'm getting

So if any one knows just how slack crawls and extracts that info.