Application using API

This would be web based application which would use API on [login to view URL] where any search string input would read [login to view URL] search results giving the app user an option to see how his own listings rank and also user would be able manage/store the data gathered also to compare saved data with new search results later. App user would need to link his website account with his Etsy account. There should be two search type options : 1. To use search field for general search result and 2. Dropdown categories where you would be able to choose under what category you would like the application to do the search. All of this has to happen under my new website and the app user would use his Etsy account to give permission to the website application to access his account details (only what Etsy allows under use of API) on Etsy.com.