System prompt linter

Paste a system prompt, then press Check prompt.

Nothing here is sent to any model; every rule is plain JavaScript running in this tab, which is what makes the score usable as a review gate between prompt versions. Know what the rules cannot see: contradictions only register when both sides share wording, so "always refund" against "reject every refund request" passes; legitimate exceptions are flagged until you merge them into one rule; and the score compares versions of the same prompt, not different prompts against each other.