The idea would seem to be to give instructions to your agent (Claude Code, etc) to use this tool to discover the chunks of code (not entire source files) it needs to look at to modify a particular function. You could put these instructions on how/when to use scribe someplace like .claude/rules/scribe.md
I assume this is meant to work as an override to Claude Code's normal operation where it reads entire source files into context (not sure on details as to how CC decides which files are relevant if developer hasn't explicitly told it), so if you asked CC to do something that matches the instructions you'd put in scribe.md it would run scribe, send the output (code chunks and file locations) to Claude AI, which would then base it's edit requests on that.
It's not obvious if this --covering-set command is the only one scribe currently supports, or if it has other ones to output code chunks relevant for other use cases.
Has anyone tried scribe for larger scale projects, and green field development?