Here are some of the more useful calls in the eBay Trading API :
*Token and Session Management*
- FetchToken
- GetSessionID
- GetTokenStatus
- RevokeToken
*API Management*
- GetApiAccessRules
*Special*
- GetContextualKeywords - AdContext - requires eBay approval
- GetSearchResults - Not usable after 2010; use Finding API
- PlaceOffer - Bid on an auction or buy it now
*Category Management*
- GetCategories - Returns category hierarchy
- GetCategory2CS - Map categories to corresponding characteristic sets
- GetCategoryFeatures - Returns a lot of data
- GetCategoryListings - Get items listed in a category; filtering (location...)
- GetCategoryMappings - Map inactive categories to active ones
- GetCategorySpecifics - Get custom Item Specifics (key/value pairs)
- GeteBayDetails - Meta-data for the specified eBay site (US, DE,...)
- GetItem - Get info similar to eBay's View item page
- GetItemShipping - Shipping calculator; return shipping cost estimates
- GetItemTransactions - Transactions for a given item
- GetPopularKeywords - Use with CategoryID to find popular buyer searches
- GetProductFamilyMembers - Use with GetProductSearchResults; returns all versions
- GetProductFinder - Get data about what you can search on. Use data as input to GetProductSearchResults
- GetProducts - Searches stock information and reviews for products
- GetSuggestedCategories - Return list of categories with items whose titles contain keywords
- GetUser - Get data for a registered eBay user
- GetUserContactDetails - Get contact info for a specified user
- GetWantItNowPost - Similar to GetWantItNowSearchResults, but provides descripton
- GetWantItNowSearchResults - Get Want It Now posts that match keywords or CategoryID
*Seller-Oriented Calls*
- GetCrossPromotions - To use seller must own an eBay Store
- GetItemRecommendations - For sellers; recommended listing changes
- GetProductSearchResults - Selling counterpart to GetProducts; "Sell Your Item"
- GetProductSellingPages - Selling counterpart to GetProducts; present catalog info to a seller
- GetPromotionalSaleDetails - Get info about promo sales set up by an eBay store owner
- GetPromotionRules - To use, you must be a seller and store owner