Hey @Suraj_Chougule - the payment session request that Shopify sends to your offsite payments app only includes the total amount, currency, and customer details (email, billing/shipping address). It doesn’t include any line item data like product descriptions, prices, or quantities.
Payments apps are restricted to the Payments Apps API only, so you can’t call the Admin API to fetch order details, and companion apps aren’t permitted either per the payments extension requirements.
This exact question was covered in this thread where it was confirmed as a current platform limitation. Feedback has been shared with the product team, and I’ll add your use case to that as well.