1. A non-transitory computer-readable storage medium comprising computer-readable instructions that, in response to execution, cause a computing system to perform operations, comprising: receiving information indicative of initial entities for content and initial scores associated with the initial entities from one or more content annotation sources; aggregating the information indicative of initial entities for content and initial scores associated with the initial entities received from the one or more content annotation sources; defining a range of values; mapping the initial scores to respective values within the defined range, the mapping producing calibrated scores within the defined range; selecting weights based on joint performance conditions; applying the selected weights to the calibrated scores within the defined range to produce weighted, calibrated scores; selecting a linear aggregation model from among a plurality of linear aggregation models; combining the weighted, calibrated scores based on the selected linear aggregation model to generate a final score; and determining whether to annotate the content with at least one of the initial entities based on a comparison of the final score and a defined threshold value.