In one embodiment, a method includes receiving a user input including an ambiguous mention by a user from the user's client system, analyzing the user input to identify intents and slots based on a natural-language understanding module, where at least one slot is an ambiguous slot corresponding to the ambiguous mention, identifying candidate entities corresponding to the ambiguous slot, ranking the candidate entities based on the user's user profile data, sending to the user's client system instructions for prompting the user to select a candidate entity from a set of candidate entities having a rank greater than a threshold rank, where the selected candidate entity is resolved to the ambiguous slot, and storing the selected candidate entity together with the ambiguous mention as a mention-entity pair as part of the user profile data responsive to receiving the selection from the user.