System prompt linter
Paste a system prompt and get instant warnings — contradictions, vague words, missing format spec, token waste. Your prompt never leaves the browser.
System prompt
Not stored in the URL or sent anywhere — linting runs locally in your browser.
Findings
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Rule-based checks only — no LLM reads your prompt. Good for catching obvious mistakes, not for judging whether instructions will work in production.
About this tool
System prompts are code you never typecheck. This linter runs simple heuristics: length bounds, keyword contradictions, vague phrases, missing output format, politeness filler, ALL CAPS ratio, duplicate sentences, unclosed ``` fences, and multiple "you are…" personas.
It is not an AI review and it cannot know your product. A clean lint pass does not mean the prompt works — it means you avoided a few common footguns. Always test on real inputs.
Token estimate uses ~4 characters per token — close enough for English prose, wrong for code-heavy prompts. Treat it as a ballpark.