Last updated on October 23rd, 2026 at 12:44 pm
good AI coding instructions define scope, permission, safety, and verification in concrete terms. Vague requests such as “do it safely” or “future-proof it” sound useful, but they leave too much room for interpretation.
Make each rule specific
A compact set of guardrails works best when every rule tells the coding assistant what action is allowed, what is restricted, or what evidence is required.
Rules should also avoid contradictions. For example, “never edit the plan” conflicts with “write the plan.” A clearer rule is: read the plan first, then update it only when explicitly requested.
Five useful guardrail groups
- Scope: Change only what was requested. Do not add unrelated features, dependencies, or abstractions.
- Planning: Read the relevant documentation first. State assumptions, risks, and blockers before implementation.
- Implementation: Follow existing patterns and choose the simplest maintainable solution.
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Safety: Ask before destructive or irreversible actions. Never expose, log, or commit secrets.
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Verification: Run focused tests and checks. Do not claim success without evidence.
Replace vague rules with testable instructions
Problem: “Do not over-engineer” is subjective.
Fix: “Prefer the smallest change that meets the stated requirements, and do not introduce a new abstraction unless existing code cannot support the change.”
Problem: “Make it future-proof” can encourage unnecessary complexity.
Fix: “Preserve backward compatibility and leave clear extension points only where a known requirement needs them.”
Problem: “Reply briefly” may hide important risks.
Fix: “Keep the response concise, but always report risks, verification results, and remaining work.”
A practical starter checklist
- Inspect the relevant code and documentation before changing anything.
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Confirm the exact files and behavior in scope.
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Make small, reversible changes that match existing conventions.
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Run the most focused useful tests, formatting, and static analysis.
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Report what changed, what was verified, and one concrete next action.
Common mistake
Too many overlapping rules can make the instructions harder to follow. Combine duplicates and keep the strongest version. A short rule that changes behavior is more useful than several slogans that repeat the same idea.
Make completion observable
A useful task instruction names the behavior that should change and the evidence that will demonstrate it. For example: “An expired reset link must show the existing error page; run the relevant request test and report its result.” Repository instructions reduce ambiguity, but they do not replace reviewing the diff or verifying external actions.
Write AI coding guardrails as observable actions, not broad intentions. The next action is to turn your current instruction list into five sections: scope, planning, implementation, safety, and verification.