0.5 cups of agave nectar is a common measurement for sweetening recipes. It is about the size of a tennis ball.

In kitchen measures
8 tablespoons
24 tsp · 8 tbsp · 0.5 cups
about the size of a tennis ball
Agave nectar typically ranges 1.35–1.45 g/mL depending on how it's packed. A firmly packed scoop weighs more.