Processing tools are little applications that extend the PDE. Processing comes with a standard set of tools: a color selector, a tool to create fonts, a tool to create movies, and some other useful things.
There is an overview of available tools on the Processing website at http://processing.org/reference/tools/. This overview includes all standard tools and tools made by people from the Processing community. At the moment, there aren't that many tools available, but the number of quality tools might grow in the future.
Processing 2 has a new feature to install tools in an easy way: the Tool Manager. You can find the Tool Manager by going to Tools | Add Tool…. The Tool Manager works the same way as the Library Manager we've discussed in the Installing libraries recipe. Just like with libraries, not all tools are available in the Tool Manager. If you find a tool online, you can install it manually in the tools
directory. This procedure is the same as installing a library manually. The Tool Manager looks as shown in the following screenshot: