When to use which

Here's the decision framework:

• Knowledge = what Devin should remember. Always-on, org-level; aim for roughly 70 to 80% relevance in its scope.
• Playbooks = what Devin should do repeatedly. Invocable task templates, shared org-wide.
• Skills = how Devin operates in this specific repo. Repo-scoped procedures in .agents/skills/.
• Rules = what Devin must or must not do in this repo. Always-on constraints in AGENTS.md.

When you're unsure, reach for Skills and Rules first: they live in the repo alongside your code, where any AI tool can read them, making them the most durable. Reserve Knowledge and Playbooks for org-wide instructions and repeatable procedures that aren't tied to a single repo.

Start small and let it compound. Add a knowledge item when you repeat yourself. Write a playbook when a task recurs. Capture a rule when Devin gets something wrong. Every addition makes the next session more autonomous and shorter, which means fewer ACUs.