The spirit of cooperation

I understand that the listing agent represents the seller's best interests, and the buyers agent represents the buyers best interests, but who's interests are you representing when you flat out lie to the other agent working the transaction? And not just one little white lie. This agent gave me 3 different stories regarding repairs made to the property. This agent never did tell me the truth about the situation, I found out on my own when I met the person who did the repairs.  Maybe it's just me, but I really believe that cooperation makes everything run much more smoothly. What was this agent hoping to accomplish? What was the point of lying? All it did was create unnecessary tension between him & myself and the buyer & seller. We managed to close the sale, but I'm still baffled as to why one agent would flat out lie to the other agent.