Here’s a getting started post in the scripting subforum.
You’ll find most of the info behind the link in the linked post, though, including how to enable the scripting terminal/editor in renoise. I’d say this is probably how you would want to view the tool script(s?). If you just want to browse the tool files with a text editor, rename the gridpie.xrnx into gridpie.zip and extract. The xrnx files are just zips in disguise.