Afghani explains the deal from an Afghan POV - ie bargaining for a carpet/ resolving problems
Kerry's role - a trusted elder. Very good read - http://www.theatlantic.com/international/archive/2014/09/afghanistan-politics-carpets-election-ghani-abdullah/380924/
This really is a remarkable diplomatic achievement. For all the NYT, using American logic, complained about whether it was really "Constitutional" - this story shows that - more importantly - it was consistent with Afghan culture.
Wherever this goes, it is useful to remember where things were going (essentially over the cliff) before the agreement happened. This will give Afghanistan a chance - and the outcome will be what they make of it. It seems lucky to me that they found a wise, trusted elder willing to listen and hear - not just what they wanted - but the minimum they would accept.