How do I update inventory and shipping tracking information through SP-API as a Seller?

I need to retrieve orders through Amazon's Seller SP-API, regularly update the inventory for all of our SKUs that are listed on Amazon as well as update Amazon with the shipment tracking number and status when the order is shipped out.

So far, I am using the orders-api to retrieve all the needed data on the order.

I have not found a straightforward way to update inventory for a SKU or update the shipment tracking number when the order is shipped out.

This is for a Seller, not a Vendor. The products are all stored in the seller's warehouse, not at Amazon.

What API endpoint should I be using that will allow the updating of inventory as well as updating of shipping information when the order is shipped out?

I've gone through every API endpoint listed here.

I have an ongoing Support Case with Amazon for the past 10 days and am currently on hold with Amazon Support for the past hour and the person on the other end of the line said they don't know either and have to find out.

Does anyone know what API endpoint / operation will do this?

Solution

As far as I am aware, the most reliable way currently to update listings and add shipping data is through the Feeds API. There are many different types of feeds you can submit to Amazon, you can see them all here.

To update a listing's inventory, use the POST_INVENTORY_AVAILABILITY_DATA feed.
To add shipment and tracking information, use the POST_ORDER_FULFILLMENT_DATA feed.

Feeds have been around for a while and are commonly used in the MWS API. So, you should be able to find plenty of resources online on how to submit a feed. Check out the use case guide for a walkthrough on how it's done.

For some product types, you can use the Listings Items API to update product attributes, including (I believe) inventory. This would not apply to shipping however.