Examples of techniques for constructing, evaluating, and improving a search string for retrieving images are disclosed. In one example implementation according to aspects of the present disclosure, a computer-implemented method includes receiving, by a processing device, a plurality of images returned as results to an executed search string in the form of a tuple including an item class, an action and an actor. The method further includes generating, by the processing device, a collection similarity score by comparing at least one of the plurality of images to at least one other of the plurality of images. The method further includes determining, by the processing device, whether the collection similarity score exceeds a collection threshold. The method further includes, based at least in part on determining that the similarity score does not exceed the collection threshold, indicating that the search string is ineffective at indicating the item use.