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I was frustrated with the lack of clear advice on setting up copilot_instructions.md. Most guides are vague, or worse, generic AI slop that *hurts* Copilot's performance. So I experimented and found better ways to make Copilot *actually helpful*. 🧵

Most devs either skip copilot_instructions.md or fill it with generic fluff. But irrelevant instructions waste Copilot’s context space and reduce output quality. Focus on non-obvious details: unique constraints, domain rules, and project specifics.

Some essential sections to include: - Summary: What the project does, briefly. - Terminology: Domain-specific terms Copilot can’t infer. - Architecture: Key files and why things are structured this way. - Task planning: Steps Copilot should follow before coding.

Most advice skips this: Be model-specific. If Copilot repeatedly makes the same mistakes (e.g., overly verbose code or missing edge cases), include correctional hints in your file. Example: "Focus on simplicity, avoid over-comprehensive solutions."

Agent mode tip: Add clear instructions for automating checks like "npm run lint" or "npm run test". With these in your file, Copilot Agent can run the commands, fix errors, and iterate until all checks pass without constant back-and-forth.