The Marketplace Insights API is part of the eBay Buy APIs. It provides the ability to search for sold items on eBay by keyword, GTIN, category, and product and returns the of sales history of those items.
Note:
This is a 
(Limited Release) API available only to select developers approved by business units. For information on how to obtain access to this API in production, see the Buy APIs Requirements.
Technical overview
This API uses the following resource:
- item_sales - Retrieves the sales history of eBay items that have been sold up to 90 days in the past.
Business use cases
The Marketplace Insights API gives you the ability to search for sold items on eBay by keyword, GTIN, ePID (eBay Product ID), and categories and returns the of sales history of those items.
API restrictions
The following are the constraints for the Marketplace Insights API.
Regional/site constraints
For a list of the supported eBay sites for all the Buy APIs, see Buy API Support by Marketplace.
To specify the site, set the X-EBAY-C-MARKETPLACE-ID request header to the site. For example:
X-EBAY-C-MARKETPLACE-ID = EBAY_GB
Item sales history range
The sales history range is up to 90 days in the past.
Category restriction
This API does not support all of the eBay categories. Partner allowed categories need to be vetted by business and then whitelisted for that partner.