Verdict
Codebase Design gives agents a compact architectural vocabulary centered on deep modules, narrow interfaces, locality, and testable seams. It improves design conversations without pretending that a generic architecture pattern fits every repository.
Best for
New module boundaries, refactors with growing surface area, and codebases where agents keep spreading one behavior across many shallow abstractions.
Keep in mind
Deep modules require domain judgment; the skill can identify a promising seam but cannot prove that the chosen boundary matches future product change.
Example task
Design a single pricing module that hides provider rules and exposes the smallest interface needed by checkout, invoices, and previews.