No. We can get the agave nectar here now but I have not looked into it - I routinely use honey.
Irrespective of that, the back sweetening principle is the same i.e. check the finished gravity, then adding small amounts of the sweetening agent, stirring gently to mix it in, check the gravity again and taste.
That way you will achieve the level of sweetness you prefer. Plus its easy to add more if required, its hard to remove if you added too much (by adding to much in one go).
This presumes you've completed all the usual steps - clearing, stabilising, etc, prior to back sweetening.......