The Austro-Hungary 10-point ultimatum to Serbia [1914]?

Yes, you're right. Serbia did not agree to the ultimatum as it was unfair and it was only an excuse by the Austro-Hungarians to start the war. During those years Europe was filled with tension between its countries, the ination was only a spark, so to speak. Then countries took sides, and the war erupted. Try to think of it as a barrel. The barrel was filling with water and the ination put in that extra cup of water that made all of the water overflow. Okay, maybe not the best comparison, but you get it, right? You're totally right about the wanting an excuse part. They knew Serbia couldn't accept the unfair ultimatum, they made it that way purposefully, so that they'd have a reason to declare war on them. Hope I helped! :)