--- title: "Recommend Items to User" method: POST path: "/{databaseId}/recomms/users/{userId}/items/" tags: ["Recommendations"] --- # Recommend Items to User `POST /{databaseId}/recomms/users/{userId}/items/` Based on the user's past interactions (purchases, ratings, etc.) with the items, recommends top-N items that are most likely to be of high value for the given user. The most typical use cases are recommendations on the homepage, in some "Picked just for you" section, or in email. The returned items are sorted by relevance (the first item being the most relevant). Besides the recommended items, also a unique `recommId` is returned in the response. It can be used to: - Let Recombee know that this recommendation was successful (e.g., user clicked one of the recommended items). See [Reported metrics](https://docs.recombee.com/admin_ui#reported-metrics). - Get subsequent recommended items when the user scrolls down (*infinite scroll*) or goes to the next page. See [Recommend Next Items](https://docs.recombee.com/api#recommend-next-items). It is also possible to use POST HTTP method (for example in the case of a very long ReQL filter) - query parameters then become body parameters. ## Path parameters - `databaseId` string, required - `userId` string, required ## Request body - RecommendItemsToUserParameters - `count` integer, required — Number of items to be recommended (N for the top-N recommendation). - `scenario` string — Scenario defines a particular application of recommendations. It can be, for example, "homepage", "cart", or "emailing". You can set various settings to the [scenario](https://docs.recombee.com/scenarios) in the [Admin UI](https://admin.recombee.com). You can also see the performance of each scenario in the Admin UI separately, so you can check how well each application performs. The AI that optimizes models to get the best results may optimize different scenarios separately or even use different models in each of the scenarios. - `cascadeCreate` boolean — If the user does not exist in the database, returns a list of non-personalized recommendations and creates the user in the database. This allows, for example, rotations in the following recommendations for that user, as the user will be already known to the system. - `returnProperties` boolean — With `returnProperties=true`, property values of the recommended items are returned along with their IDs in a JSON dictionary. The acquired property values can be used to easily display the recommended items to the user. Example response: ```json { "recommId": "ce52ada4-e4d9-4885-943c-407db2dee837", "recomms": [ { "id": "tv-178", "values": { "description": "4K TV with 3D feature", "categories": ["Electronics", "Televisions"], "price": 342, "url": "myshop.com/tv-178" } }, { "id": "mixer-42", "values": { "description": "Stainless Steel Mixer", "categories": ["Home & Kitchen"], "price": 39, "url": "myshop.com/mixer-42" } } ], "numberNextRecommsCalls": 0 } ``` - `includedProperties` string[] — Allows specifying which properties should be returned when `returnProperties=true` is set. The properties are given as a comma-separated list. Example response for `includedProperties=description,price`: ```json { "recommId": "a86ee8d5-cd8e-46d1-886c-8b3771d0520b", "recomms": [ { "id": "tv-178", "values": { "description": "4K TV with 3D feature", "price": 342 } }, { "id": "mixer-42", "values": { "description": "Stainless Steel Mixer", "price": 39 } } ], "numberNextRecommsCalls": 0 } ``` - `filter` string — Boolean-returning [ReQL](https://docs.recombee.com/reql) expression, which allows you to filter recommended items based on the values of their attributes. Filters can also be assigned to a [scenario](https://docs.recombee.com/scenarios) in the [Admin UI](https://admin.recombee.com). - `booster` string — Number-returning [ReQL](https://docs.recombee.com/reql) expression, which allows you to boost the recommendation rate of some items based on the values of their attributes. Boosters can also be assigned to a [scenario](https://docs.recombee.com/scenarios) in the [Admin UI](https://admin.recombee.com). - `logic` union - string - object - `name` string — Name of the logic that should be used - `settings` object — Parameters passed to the logic - `reqlExpressions` object — A dictionary of [ReQL](https://docs.recombee.com/reql) expressions that will be executed for each recommended item. This can be used to compute additional properties of the recommended items that are not stored in the database. The keys are the names of the expressions, and the values are the actual ReQL expressions. Example request: ```json { "reqlExpressions": { "isInUsersCity": "context_user[\"city\"] in 'cities'", "distanceToUser": "earth_distance('location', context_user[\"location\"])" } } ``` Example response: ```json { "recommId": "ce52ada4-e4d9-4885-943c-407db2dee837", "recomms": [ { "id": "restaurant-178", "reqlEvaluations": { "isInUsersCity": true, "distanceToUser": 5200.2 } }, { "id": "bar-42", "reqlEvaluations": { "isInUsersCity": false, "distanceToUser": 2516.0 } } ], "numberNextRecommsCalls": 0 } ``` - `diversity` number, double — **Expert option:** Real number from [0.0, 1.0], which determines how mutually dissimilar the recommended items should be. The default value is 0.0, i.e., no diversification. Value 1.0 means maximal diversification. - `minRelevance` 'low' | 'medium' | 'high' — **Expert option:** Specifies the threshold of how relevant must the recommended items be to the user. Possible values one of: "low", "medium", "high". The default value is "low", meaning that the system attempts to recommend a number of items equal to *count* at any cost. If there is not enough data (such as interactions or item properties), this may even lead to bestseller-based recommendations to be appended to reach the full *count*. This behavior may be suppressed by using "medium" or "high" values. In such a case, the system only recommends items of at least the requested relevance and may return less than *count* items when there is not enough data to fulfill it. - `rotationRate` number, double — **Expert option:** If your users browse the system in real-time, it may easily happen that you wish to offer them recommendations multiple times. Here comes the question: how much should the recommendations change? Should they remain the same, or should they rotate? Recombee API allows you to control this per request in a backward fashion. You may penalize an item for being recommended in the near past. For the specific user, `rotationRate=1` means maximal rotation, `rotationRate=0` means absolutely no rotation. You may also use, for example, `rotationRate=0.2` for only slight rotation of recommended items. Default: `0`. - `rotationTime` number, double — **Expert option:** Taking *rotationRate* into account, specifies how long it takes for an item to recover from the penalization. For example, `rotationTime=7200.0` means that items recommended less than 2 hours ago are penalized. Default: `7200.0`. - `expertSettings` object — Dictionary of custom options. - `returnAbGroup` boolean — If there is a custom AB-testing running, return the name of the group to which the request belongs. ## Response `200` Successful operation. - RecommendationResponse - `recommId` string, required — Id of the recommendation request - `recomms` Recommendation[], required — Obtained recommendations - `id` string, required — Id of the recommended item - `values` object — Property values of the recommended item - `reqlEvaluations` object — Dictionary of evaluated ReQL expressions specified in the request and calculated for the recommended item. The keys are the names of the ReQL expressions, and the values are the results of the evaluations. - `numberNextRecommsCalls` integer — How many times *Recommend Next Items* have been called for this `recommId` - `abGroup` string — Name of AB-testing group to which the request belongs if there is a custom AB-testing running. ## Other responses - `400` — userId does not match ^[a-zA-Z0-9_\-:@\.]+$, count is not a positive integer, filter or booster is not valid [ReQL](https://docs.recombee.com/reql) expressions, filter expression does not return boolean, booster does not return double or integer. - `404` — userId not found in the database and cascadeCreate is false. If there is no additional info in the JSON response, you probably have an error in your URL. --- [API](https://skmtc.dev/recombee/apis/recombee-api.md) · [All operations](https://skmtc.dev/recombee/apis/recombee-api/llms.txt) · [OpenAPI document](https://skmtc-service-production.skmtc.workers.dev/v1/apis/recombee/recombee-api/revisions/a9c9c33eb2e8/schema)