2006 Caravan Belt Tensioner

I don't have a Caravan, but on most vehicles, there will be a square hole in such a tab on the tensioner to fit perfectly with either a 3/8" or 1/2" square drive (as in a ratchet or breaker bar).

Or even better, as in a torque wrench (since there's a torque spec for it).

On all the ones I've seen, that hole is used only to hold tension off to create slack for removing or installing the belt. Tension was either done with a built-in tensioner spring (that was either active all the time or applied initial tension until the lock down bolt was tightened) or tension was manually adjusted with a jack screw built into the tensioner (no spring). You may be right that some vehicles use the square hole for the actual tensioning (with a torque wrench), but I have never seen that (on any of the cars I've owned).

If we're thinking of the same tab, it was used to tension the belt on