Final answer:
The Count's servant is at the Duke's residence to negotiate the Duke's prospective marriage to the Count's daughter in the poem "My Last Duchess".
Step-by-step explanation:
In the poem "My Last Duchess", the Count's servant has come to the Duke to discuss the matter of the Duke's next marriage. It is implied that the servant is there to negotiate the marriage between the Duke and the Count's daughter. This meeting is set against the backdrop of the Duke showing the servant a portrait of his former wife, who is now deceased, and discussing her character and his reasons for her demise.