Determination agent
One who determines things on behalf of contracting counterparties. To be compared and contrasted with a Calculation Agent, who calculates things on behalf of contracting counterparties.
Do calculation and determination differ?
Not as far as this correspondent can see. But that won't stop over-enthusiastic members of the bar waxing lengthily about how they do. Note the different roles played by the Calculation Agent and the Determination Agent in the 2002 ISDA Equity Derivatives Definitions.