The Agile manifesto declares that it's adherents favor Individuals and Interactions over process and tools. But all software development teams use tools, so what kind of tools match this mindset? Here's two characteristics that I see:
Agile tools are easy to replace. They provide value without increasing the cost of change. If you get locked in to a tool, you'll have to find a replacement thats MUCH better before it's worth the effort to change. 5 years could go by while you're waiting for that to happen. The more adapted you are, the less adaptable you become.
Agile tools are flexible yet simple. The best require little configuration or customization, yet can be used in hundreds of different ways (take your favorite text editor, for example).
It's a common fallacy that Agile developers don't value tools. We do. We just realize that the tools won't do our job for us, and that it's up to us to make the project succeed.