Bring 4 cups water to a boil. Pour water over the tea bags in a large heatproof mixing bowl. Let steep 6 minutes before removing the tea bags. While the tea is still hot, add a squirt or two of the agave. I usually squirt it into a small figure-eight 2 times and that is the perfect amount for lightly-sweet tea. Add four cups cold water.
When the tea is cool enough to handle, pour into your pitcher of choice and chill. Add lemon slices just before serving and, if you remember, pop your serving glasses in the freezer for a few minutes just before pouring. A chilled glass makes all the difference.