What was germany doing that made the treaty of versailles good?

Considering the Treaty of Versailles good or bad is a matter of opinion, even more so nowadays. As for what it seem like a good idea at the time, Germany entered World War 1 without being provoked- they had an agreement with the Austro-Hungarian Empire that if Austria-Hungary went to war, then Germany would as well. Austria-Hungary declared war on Serbia after their Archduke was assassinated- Germany agreed to help in that effort based upon their standing agreement- however Germany also knew that France would jump into the war, so they attacked France first.
In order to attack France, Germany couldn't attack their shared border with France without suffering a lot of casualties. Germany and France had engaged in several wars over history, so France had fortified their shared border extensively. So Germany decided that they would go through Belgium in order to attack France, bypassing that shared border. Belgium was founded as a neutral country, and their sovereignty was recognized by France, England, and others. Germany breached their border, which was seen as an act of hostility upon a neutral nation. While passing through Germany they were attacked by the Belgian troops who were effectively acting in self defense.
These acts effectively set of chain reactions that led to World War 1. France asked Britain and Russia for help in the war based upon their pre-existing alliances, and Britain was not at all happy that Germany had decided to invade Belgium when Germany wasn't directly provoked in the conflict.
As a result, everyone who felt slighted by the Germans in the conflict wanted Germany to pay war reparations and suffer many consequences. The Treaty of Versailles also required that Germany accept the blame for the war itself- in a few ways this was fair, but in many other ways it was not. Austria-Hungary was the first to declare war on another nation, not Germany. But this was how it was decided the Treaty would be set up, and Germany had lost the war pretty badly so they didn't feel they had any room to negotiate.
The Treaty was considered good as it not only "guaranteed" peace, but also punished Germany and forced them to monetarily pay other countries to repair their infrastructure which Germany had damaged. If you research the effect that treaty had on Germany, though, it's easy to see why many historians feel that this was one of the essential causes of World War 2. Although there is room for debate on that.