This tool will validate the Puppet DSL syntax. It won't actually compile a catalog or enforce any configuration state. This means that this only validates syntax. There are many ways in which a Puppet manifest may have valid syntax but be completely incorrect for your purposes and not do what you intend.
Some examples of flaws that will not be identified by this tool include:
execresources which fail to run properly.
Many other resources exist which can help make sure your code actually works as intended. Some examples are: