getRelatedCategoryItems

Note: All calls in the Merchandising API have been deprecated as of July 29, 2024, and will be decommissioned on January 6, 2025.

Retrieves recommended items from categories related to a specified category or item. If categoryId is specified, then items are returned from categories related to the given category. If itemId is specified, then items are returned from categories related to the given item's category. In either case, the response contains items from the three best matching categories. The selection of items is evenly distributed between the best matching categories. The recommended items are sorted by end time, with items ending soonest first.

The request must contain either categoryId or ItemId. If both itemId and categoryId are specified, categoryId takes precedence.

Note: In some cases, the item recommendations returned by getRelatedCategoryItems are not closely related to the item specified in the request. Refer to the getRelatedCategoryItems does not return related items thread in the eBay Shopping and Merchandising API Production System Announcements board for more information, including an ETA for when this problem will be resolved.

Input

Output

See also Samples.

The box below lists all fields that might be returned in the response. To learn more about an individual field or its type, click its name in the box (or scroll down to find it in the table below the box).

<?xml version="1.0" encoding="utf-8"?>
<getRelatedCategoryItemsResponse xmlns="http://www.ebay.com/marketplace/services">
  <!-- Call-specific Output Fields -->
  <itemRecommendations> ItemRecommendations
    <item> Item
      <bidCount> int </bidCount>
      <buyItNowPrice currencyId="string"> Amount (double) </buyItNowPrice>
      <country> string </country>
      <currentPrice currencyId="string"> Amount (double) </currentPrice>
      <globalId> string </globalId>
      <imageURL> anyURI </imageURL>
      <itemId> string </itemId>
      <originalPrice currencyId="string"> Amount (double) </originalPrice>
      <primaryCategoryId> string </primaryCategoryId>
      <primaryCategoryName> string </primaryCategoryName>
      <shippingCost currencyId="string"> Amount (double) </shippingCost>
      <shippingType> string </shippingType>
      <subtitle> string </subtitle>
      <timeLeft> duration </timeLeft>
      <title> string </title>
      <viewItemURL> anyURI </viewItemURL>
    </item>
    <!-- ... more item nodes allowed here ... -->
  </itemRecommendations>
  <!-- Standard Output Fields -->
  <ack> AckValue </ack>
  <errorMessage> ErrorMessage
    <error> ErrorData
      <category> ErrorCategory </category>
      <domain> string </domain>
      <errorId> long </errorId>
      <exceptionId> token </exceptionId>
      <message> string </message>
      <parameter name="string"> ErrorParameter (string) </parameter>
      <!-- ... more parameter values allowed here ... -->
      <severity> ErrorSeverity </severity>
      <subdomain> string </subdomain>
    </error>
    <!-- ... more error nodes allowed here ... -->
  </errorMessage>
  <timestamp> dateTime </timestamp>
  <version> string </version>
</getRelatedCategoryItemsResponse>

Return Value	Type	Occurrence	Meaning

Call-specific Output Fields [Jump to standard fields]

itemRecommendations	ItemRecommendations	Always	A list of items matching the given criteria. Item sort order is different for each call. Returned when there are items that match the search criteria.
itemRecommendations.item	Item	Conditionally, repeatable: [0..*]	Contains details for a single recommended item. Returned when there is at least one item that matches the search criteria.
itemRecommendations.item .bidCount	int	Conditionally	The number of bids that have been placed on the item.
itemRecommendations.item .buyItNowPrice	Amount (double)	Conditionally	The Buy It Now Price of the item (if any), in the currency of the site on which the item was listed. For Chinese auctions (Quantity=1, competitive bidding online auctions), Buy It Now lets a user purchase the item at a fixed price and end the auction immediately. On most sites, after a Chinese auction has bids, the listing is no longer eligible for Buy It Now. However, calls can still return the Buy It Now Price that the seller set for the listing. Use the item.bidCount field to determine whether an auction with Buy It Now has bids or not. Some eBay sites also support Buy It Now for Dutch auctions (multi- quantity, competitive bidding), where you can buy multiple items from the same listing at a fixed price, instead of bidding. On some sites, the Buy It Now option remains available for Dutch auctions even after there are bids. For fixed-price (FixedPriceItem) and Store Inventory listings (StoresFixedPrice), see currentPrice instead. Only returned if an item was listed with Buy It Now.
itemRecommendations.item .buyItNowPrice [ attribute currencyId ]	string	Always	The Buy It Now Price of the item (if any), in the currency of the site on which the item was listed. For Chinese auctions (Quantity=1, competitive bidding online auctions), Buy It Now lets a user purchase the item at a fixed price and end the auction immediately. On most sites, after a Chinese auction has bids, the listing is no longer eligible for Buy It Now. However, calls can still return the Buy It Now Price that the seller set for the listing. Use the item.bidCount field to determine whether an auction with Buy It Now has bids or not. Some eBay sites also support Buy It Now for Dutch auctions (multi- quantity, competitive bidding), where you can buy multiple items from the same listing at a fixed price, instead of bidding. On some sites, the Buy It Now option remains available for Dutch auctions even after there are bids. For fixed-price (FixedPriceItem) and Store Inventory listings (StoresFixedPrice), see currentPrice instead. Only returned if an item was listed with Buy It Now.
itemRecommendations.item .country	string	Conditionally	Two-letter ISO 3166 country code to indicate the country where the item is located. For English names that correspond to each code (e.g., KY="Cayman Islands"), see the ISO site.
itemRecommendations.item .currentPrice	Amount (double)	Conditionally	For competitive-bidding listings (Chinese and Dutch auctions), current minimum asking price (start price) or the current highest bid for the item if bids have been placed. Shows minimum bid if no bids have been placed on the item. For Basic Fixed-Price, Store Inventory, or Ad type listings, this returns the original price specified when the item was listed/re-listed or the revised price if the item was revised.
itemRecommendations.item .currentPrice [ attribute currencyId ]	string	Always	For competitive-bidding listings (Chinese and Dutch auctions), current minimum asking price (start price) or the current highest bid for the item if bids have been placed. Shows minimum bid if no bids have been placed on the item. For Basic Fixed-Price, Store Inventory, or Ad type listings, this returns the original price specified when the item was listed/re-listed or the revised price if the item was revised.
itemRecommendations.item .globalId	string	Conditionally	The site upon which the item is listed. Returns a Global ID, which is a unique identifier for combinations of site, language, and territory. For a list of possible enumeration values and how they map to eBay sites, see Global ID Values.
itemRecommendations.item .imageURL	anyURI	Conditionally	URL for a picture used as the Gallery thumbnail, if any. The image uses one of the following graphics formats: JPEG, BMP, TIF, or GIF. Only returned if the seller chose to show a gallery image.
itemRecommendations.item .itemId	string	Always	The ID that uniquely identifies the item listing. The ID is generated by eBay after an item is listed. You cannot choose or revise this value. Max length: 19.
itemRecommendations.item .originalPrice	Amount (double)	Conditionally	Original price of an item whose price a seller has reduced with the Promotional Price Display feature. Only returned if the price has been revised.
itemRecommendations.item .originalPrice [ attribute currencyId ]	string	Always	Original price of an item whose price a seller has reduced with the Promotional Price Display feature. Only returned if the price has been revised.
itemRecommendations.item .primaryCategoryId	string	Conditionally	Numeric ID of the first (or only) category in which the item is listed. (Listings can appear in more than one category.) Note: Currently, the Merchandising API calls do not return a listing's secondary category, if any. Max length: 10.
itemRecommendations.item .primaryCategoryName	string	Conditionally	Display name of the first (or only) category in which the item is listed. This is a fully qualified category breadcrumb (e.g., Computers & Networking:Laptops, Notebooks). Max length: 30.
itemRecommendations.item .shippingCost	Amount (double)	Conditionally	The shipping cost associated with the first shipping service. Only returned when shipping type is flat.
itemRecommendations.item .shippingCost [ attribute currencyId ]	string	Always	The shipping cost associated with the first shipping service. Only returned when shipping type is flat.
itemRecommendations.item .shippingType	string	Conditionally	The shipping cost model offered by the seller. Applicable values: Calculated Calculated shipping model: the cost of shipping is determined in large part by the seller-offered and buyer-selected shipping service. The seller might assess an additional fee via PackagingHandlingCosts. CalculatedDomesticFlatInternational The seller specified one or more calculated domestic shipping services and one or more flat international shipping services. Flat Flat shipping model: the seller establishes the cost of shipping and cost of shipping insurance, regardless of what any buyer-selected shipping service might charge the seller. FlatDomesticCalculatedInternational The seller specified one or more flat domestic shipping services and one or more calculated international shipping services. Free Free shipping: Seller has specified free shipping for the item. The cost of shipping is zero for the first domestic shipping service (for flat or calculated shipping). Freight Freight shipping model: The cost of shipping is determined by a third party, FreightQuote.com, based on the item location (zip code). NotSpecified The seller did not specify the shipping type.
itemRecommendations.item .subtitle	string	Conditionally	Subtitle of the item. Only returned if the seller included a subtitle for the listing. Note: Due to an eBay platform change in January 2015, this field is no longer supported for the getSimilarItems and getMostWatchedItems calls. It is returned in the response but will always be blank. Max length: 55.
itemRecommendations.item .timeLeft	duration	Conditionally	Time left before the item listing ends. The duration is represented in the ISO 8601 duration format (PnDTnHnMnS). For ended listings, the time left is P0DT0H0M0S (zero days, zero hours, zero minutes, and zero seconds).
itemRecommendations.item.title	string	Always	Name of the item as it appears in the listing or search results. Max length: 55.
itemRecommendations.item .viewItemURL	anyURI	Always	The URL of the web page where a user can view the listing. On the US site, this is called the "View Item" page. If you enabled affiliate tracking in the call, viewItemURL contains a string that includes affiliate tracking information (see the eBay Partner Network).

Standard Output Fields

ack	AckValue	Always	Indicates whether there are any errors or warnings associated with the processing of the request. Applicable values: Failure Errors occurred that prevented the request from being processed successfully. PartialFailure Reserved for future use. Success The request was processed successfully without errors or warnings. Warning The request was processed successfully, but some warnings were returned. Code so that your app gracefully handles any future changes to this list.
errorMessage	ErrorMessage	Conditionally	Information for an error or warning that occurred when eBay processed the request. Not returned when responseStatus is Success. See Errors by Number for a list of errors and warnings that can be returned by Merchandising API calls.
errorMessage.error	ErrorData	Conditionally, repeatable: [0..*]	Details about a single error.
errorMessage.error.category	ErrorCategory	Conditionally	There are three categories of errors: request errors, application errors, and system errors. Applicable values: Application An error occurred due to a problem with the request, such as missing or invalid fields. The problem must be corrected before the request can be made again. If the problem is due to something in the application (such as a missing required field), the application must be changed. Once the problem in the application or data is resolved, resend the corrected request to eBay. Request An error occurred due to a problem with the request, such as invalid or missing data. The problem must be corrected before the request can be made again. If the problem is a result of end-user data, the application must alert the end-user to the problem and provide the means for the end-user to correct the data. Once the problem in the data is resolved, resend the request to eBay with the corrected data. System Indicates that an error has occurred on the eBay system side, such as a database or server down. An application can retry the request as-is a reasonable number of times (eBay recommends twice). If the error persists, contact Developer Technical Support. Once the problem has been resolved, the request may be resent in its original form. Code so that your app gracefully handles any future changes to this list.
errorMessage.error.domain	string	Conditionally	Name of the domain upon which the error occurred. Domains include: Marketplace A business or validation error occurred for the Merchandising Service. SOA An exception occurred in the framework.
errorMessage.error.errorId	long	Conditionally	A unique code that identifies the particular error condition that occurred. Your application can use error codes as identifiers in your customized error-handling algorithms.
errorMessage.error.exceptionId	token	Conditionally	Unique identifier for an exception associated with an error.
errorMessage.error.message	string	Conditionally	A detailed description of the condition that resulted in the error.
errorMessage.error.parameter	ErrorParameter (string)	Conditionally, repeatable: [0..*]	Some warning and error messages return one or more variables that contain contextual information about the error. This is often the field or value that triggered the error.
errorMessage.error.parameter [ attribute name ]	string	Conditionally	Some warning and error messages return one or more variables that contain contextual information about the error. This is often the field or value that triggered the error.
errorMessage.error.severity	ErrorSeverity	Conditionally	Indicates whether the error caused the request to fail (Error) or not (Warning). If the request fails and the source of the problem is within the application (such as a missing required element), please change the application before you retry the request. If the problem is due to end- user input data, please alert the end-user to the problem and provide the means for them to correct the data. Once the problem in the application or data is resolved, you can attempt to re- send the request to eBay. If the source of the problem is on eBay's side, you can retry the request as-is a reasonable number of times (eBay recommends twice). If the error persists, contact Developer Technical Support. Once the problem has been resolved, the request may be resent in its original form. When a warning occurs, the error is returned in addition to the business data. In this case, you do not need to retry the request (as the original request was successful). However, depending on the cause or nature of the warning, you might need to contact either the end user or eBay to effect a long term solution to the problem to prevent it from reoccurring in the future. Applicable values: Error The request that triggered the error was not processed successfully. When a serious application-level error occurs, the error is returned instead of the business data. Warning The request was processed successfully, but something occurred that may affect your application or the user. For example, eBay may have changed a value the user sent in. In this case, eBay returns a normal, successful response and also returns the warning. Code so that your app gracefully handles any future changes to this list.
errorMessage.error.subdomain	string	Conditionally	Name of the subdomain upon which the error occurred. Subdomains include: Merchandising The error is specific to the Merchandising service. MarketplaceCommon The error is common to all Marketplace services.
timestamp	dateTime	Always	This value represents the date and time when eBay processed the request. The time zone of this value is GMT and the format is the ISO 8601 date and time format (YYYY-MM-DDTHH:MM:SS.SSSZ). See the "dateTime" type for information about this time format and converting to and from the GMT time zone.
version	string	Always	The version of the response payload schema. Indicates the version of the schema that eBay used to process the request. Developer Technical Support may ask you for the version value when you work with them to troubleshoot issues.

Samples

New to making API calls? Please see Making a Call.

Note: Some item IDs, user IDs, or other data in these samples might no longer be active on eBay. If necessary, you can substitute current eBay data in your requests.

Available samples:

Basic Call ↓ - Retrieves items from categories related to the category for the specified item.
Specifying a Category ↓ - Retrieves items from categories related to the specified category.

Sample: Basic Call

Retrieves items from categories related to the category for the specified item.

Description

The user b*********r has an item he's interested in and he wants to see some recommended items from related categories.

Input

The category within which the specified itemId is listed is used to determine the related categories.

URL format. See also the non-wrapped version of this URL. For results in a format other than XML, 
specify a different value for responseencoding.

https://svcs.ebay.com/MerchandisingService?
   OPERATION-NAME=getRelatedCategoryItems&
   SERVICE-NAME=MerchandisingService&
   SERVICE-VERSION=1.1.0&
   CONSUMER-ID=YourAppID&
   RESPONSE-DATA-FORMAT=XML&
   REST-PAYLOAD&
   maxResults=3&
   itemId=1**********5

Here is the same input in XML format. Note that this does not include standard values.

XML format.

<?xml version="1.0" encoding="UTF-8"?>
<getRelatedCategoryItems xmlns="https://www.ebay.com/marketplace/services">
  <maxResults>3</maxResults>
  <itemId>1**********5</itemId>
</getRelatedCategoryItems>

Output

The response contains a list of recommended items from which b*********r can choose. The current price and shipping costs are returned for each item, along with basic information about the listing, such as itemId, title, and time left. The viewItemURL links to the View Item page.

XML format.
<?xml version="1.0" encoding="UTF-8"?>
<getRelatedCategoryItemsResponse xmlns="https://www.ebay.com/marketplace/services" xmlns:sct="https://www.ebay.com/soaframework/common/types">
  <ack>Success</ack>
  <version>1.1.0</version>
  <timestamp>2008-08-15T16:09:35.113-07:00</timestamp>
  <itemRecommendations>
    <item>
      <itemId>3********2</itemId>
      <title>Lionel 76 Boulevard Lamps Cello Window BOX ONLY</title>
      <viewItemURL>
        https://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3193577262&ih=018&category=4
        146&_trksid=_trkparms=algo
      </viewItemURL>
      <globalId>EBAY-US</globalId>
      <timeLeft>P14DT17H52M38S</timeLeft>
      <primaryCategoryId>220</primaryCategoryId>
      <primaryCategoryName>Toys & Hobbies</primaryCategoryName>
      <buyItNowPrice currencyId="USD">35.0</buyItNowPrice>
      <country>US</country>
      <imageURL>https://thumbs.ebaystatic.com/pict/3********2_3.jpg</imageURL>
      <shippingCost currencyId="USD">3.55</shippingCost>
      <shippingType>Flat</shippingType>
    </item>
    <item>
      <itemId>5********6</itemId>
      <title>MTH Premier NYC Reefer Car...From Set</title>
      <viewItemURL>
        https://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=5928873256&ih=011&category=4
        730&_trksid=_trkparms=algo
      </viewItemURL>
      <globalId>EBAY-US</globalId>
      <timeLeft>P22DT23H31M34S</timeLeft>
      <primaryCategoryId>220</primaryCategoryId>
      <primaryCategoryName>Toys & Hobbies</primaryCategoryName>
      <buyItNowPrice currencyId="USD">33.0</buyItNowPrice>
      <country>US</country>
      <imageURL>https://thumbs.ebaystatic.com/pict/5********6_3.jpg</imageURL>
      <shippingType>NotSpecified</shippingType>
    </item>
    <item>
      <itemId>5********4</itemId>
      <title>1972-3 LIONEL TRAINS CANADIAN CATALOG MINT NR</title>
      <viewItemURL>
        https://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=5979899154&ih=010&category=4
        147&_trksid=_trkparms=algo
      </viewItemURL>
      <globalId>EBAY-US</globalId>
      <timeLeft>P9DT13H14M39S</timeLeft>
      <primaryCategoryId>220</primaryCategoryId>
      <primaryCategoryName>Toys & Hobbies</primaryCategoryName>
      <buyItNowPrice currencyId="USD">14.95</buyItNowPrice>
      <country>US</country>
      <imageURL>https://thumbs.ebaystatic.com/pict/5********4_2.jpg</imageURL>
      <shippingType>NotSpecified</shippingType>
    </item>
  </itemRecommendations>
</getRelatedCategoryItemsResponse>

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Sample: Specifying a Category

Retrieves items from categories related to the specified category.

Description

The user b*********r is browsing listings within a specific category, and he wants to see some recommended item from related categories.

Input

The related categories are determined from the specified categoryId.

URL format. See also the non-wrapped version of this URL. For results in a format other than XML, 
specify a different value for responseencoding.

https://svcs.ebay.com/MerchandisingService?
   OPERATION-NAME=getRelatedCategoryItems&
   SERVICE-NAME=MerchandisingService&
   SERVICE-VERSION=1.1.0&
   CONSUMER-ID=YourAppID&
   RESPONSE-DATA-FORMAT=XML&
   REST-PAYLOAD&
   maxResults=3&
   categoryId=267

Here is the same input in XML format. Note that this does not include standard values.

XML format.

<?xml version="1.0" encoding="UTF-8"?>
<getRelatedCategoryItems xmlns="https://www.ebay.com/marketplace/services">
  <maxResults>3</maxResults>
  <categoryId>267</categoryId>
</getRelatedCategoryItems>

Output

XML format.
<?xml version="1.0" encoding="UTF-8"?>
<getRelatedCategoryItemsResponse xmlns:sct="https://www.ebay.com/soaframework/common/types" xmlns="https://www.ebay.com/marketplace/services">
  <ack>Success</ack>
  <version>1.1.0</version>
  <timestamp>2008-08-15T15:13:32.994-07:00</timestamp>
  <itemRecommendations>
    <item>
      <itemId>3********2</itemId>
      <title>Lionel 76 Boulevard Lamps Cello Window BOX ONLY</title>
      <viewItemURL>
        https://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3193577262&ih=018&category=4
        146&_trksid=_trkparms=algo
      </viewItemURL>
      <globalId>EBAY-US</globalId>
      <timeLeft>P14DT17H51M39S</timeLeft>
      <primaryCategoryId>220</primaryCategoryId>
      <primaryCategoryName>Toys & Hobbies</primaryCategoryName>
      <buyItNowPrice currencyId="USD">35.0</buyItNowPrice>
      <country>US</country>
      <imageURL>https://thumbs.ebaystatic.com/pict/3********2_3.jpg</imageURL>
      <shippingCost currencyId="USD">3.55</shippingCost>
      <shippingType>Flat</shippingType>
    </item>
    <item>
      <itemId>5********6</itemId>
      <title>MTH Premier NYC Reefer Car...From Set</title>
      <viewItemURL>
        https://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=5928873256&ih=011&category=4
        730&_trksid=_trkparms=algo
      </viewItemURL>
      <globalId>EBAY-US</globalId>
      <timeLeft>P22DT23H30M35S</timeLeft>
      <primaryCategoryId>220</primaryCategoryId>
      <primaryCategoryName>Toys & Hobbies</primaryCategoryName>
      <buyItNowPrice currencyId="USD">33.0</buyItNowPrice>
      <country>US</country>
      <imageURL>https://thumbs.ebaystatic.com/pict/5********6_3.jpg</imageURL>
      <shippingType>NotSpecified</shippingType>
    </item>
    <item>
      <itemId>5********4</itemId>
      <title>1972-3 LIONEL TRAINS CANADIAN CATALOG MINT NR</title>
      <viewItemURL>
        https://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=5979899154&ih=010&category=4
        147&_trksid=_trkparms=algo
      </viewItemURL>
      <globalId>EBAY-US</globalId>
      <timeLeft>P9DT13H13M40S</timeLeft>
      <primaryCategoryId>220</primaryCategoryId>
      <primaryCategoryName>Toys & Hobbies</primaryCategoryName>
      <buyItNowPrice currencyId="USD">14.95</buyItNowPrice>
      <country>US</country>
      <imageURL>https://thumbs.ebaystatic.com/pict/5********4_2.jpg</imageURL>
      <shippingType>NotSpecified</shippingType>
    </item>
  </itemRecommendations>
</getRelatedCategoryItemsResponse>

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Change History

Change Date	Description
1.5.0 2015-01-23	itemFilter (deprecated): Due to an eBay platform change in January 2015, the itemFilter type, which lets you restrict results to only items available in the World of Good marketplace, is no longer supported.
1.4.0 2010-03-03	maxResults (modified): Increased maximum allowed results from 20 to 50. itemFilter (added): Lets you restrict results to only items available in the World of Good marketplace.
1.1.0 2008-08-12	version (added): The version of the schema eBay used to process the request. timestamp (added): The date and time when eBay processed the request.
1.0.0 2008-06-11	(added) New call

affiliate	Affiliate	Optional	Container for affiliate details. eBay uses the specified affiliate details to build a View Item URL and Product URL string in the response that includes your affiliate tracking information in the correct format. When a user clicks through these URLs to eBay and performs certain tasks, you may get an affiliate commission. See the eBay Partner Network for information about commissions.
affiliate.customId	string	Optional	Need not be specified. You can define an AffiliateUserID (up to 256 characters) if you want to leverage it to better monitor your marketing efforts. If you are using the eBay Partner Network, and you provide an AffiliateUserID, the tracking URL returned by eBay Partner Network will contain the AffiliateUserID, but it will be referred to as a "customid".
affiliate.networkId	string	Optional	Specifies your tracking partner for affiliate commissions. Affiliates earn money from eBay for driving traffic to eBay. Required if you specify a TrackingID. Depending on your tracking partner, specify one of the following values. Not all partners are valid for all sites. For PlaceOffer, only eBay Partner Network and Mediaplex are valid: 2 = Be Free 3 = Affilinet 4 = TradeDoubler 5 = Mediaplex 6 = DoubleClick 7 = Allyes 8 = BJMT 9 = eBay Partner Network For information about commissions, see the eBay Partner Network.
affiliate.trackingId	string	Optional	The value you specify is obtained from your tracking partner. For eBay Partner Network, the TrackingID is the Campaign ID ("campid") provided by eBay Partner Network. A Campaign ID is a 10-digit, unique number to be used for associating traffic. A Campaign ID is valid across all programs to which you have been accepted. Another example is the Affiliate ID given to you by TradeDoubler.
maxResults	int	Optional	Specifies the maximum number of entries to return in a single call. If the number of entries that can be returned is less than the value you specify, the lower number is returned. Values less than 1 or greater than 50 (or 20 in the case of getTopSellingProducts) will be ignored. Min: 1. Max: 50. Default: 20.

categoryId	string	Conditional	Specifies the category used to determine related categories from which to retrieve item listings. This field takes the same category ID data as used with other eBay APIs. Category IDs are site-specific. If the specified category ID doesn't match an existing category for the site, an invalid-category error message is returned. To determine valid categories, you can use either the Shopping API or the Trading API. In the Shopping API, use the FindItemsAdvanced call with the CategoryHistogram value in the IncludeSelector field to retrieve matching category information. In the Trading API, use calls like GetCategories and GetCategoryFeatures to determine valid values for the site. Max length: 10. See: FindItemsAdvanced documentation for information on retrieving a category histogram. GetCategories documentation for information on retrieving categories. GetCategoryFeatures documentation for information on retrieving category details.
itemId	string	Conditional	The ID of an active item listing. Related categories are determined from the primary category in which the item is listed. If both categoryId is also specified, it takes precedence. Max length: 19.