Use nox when an agent needs a repository-native way to define and run repeatable Python automation sessions such as tests, lint, docs, or build steps across controlled environments. Invoke this instead of using ad hoc shell commands normally when the job is specifically to execute named automation sessions from a versioned noxfile, not to browse a generic task runner. The scope boundary is concrete: declare sessions in Python, provision their environments, and run the same coded workflow on demand, which is narrow enough to be a reusable skill rather than a plain CLI listing.