Instruction Following Checker

Verify that LLM output follows each instruction in your prompt.

Extracts imperative instructions from your prompt (must, should, do not, always, never, only) and checks the LLM output against each one heuristically. Flags likely violations like banned words, missing requirements, and length limits so you can audit compliance fast. It runs free in your browser on Gera Tools, with nothing uploaded.

Last updated Source: Gera Tools

How does it find instructions?

It scans each sentence of the prompt for imperative cue words like must, should, do not, never, always, and only, plus length and format constraints. Each matching sentence becomes one checklist item.

A long prompt can carry a dozen instructions — must include a disclaimer, never mention competitors, keep it under 100 words, always end with a CTA. Models miss some of these surprisingly often. This checker extracts the instructions from your prompt and audits the output against each, so you can see compliance at a glance instead of re-reading both texts line by line.

Why models miss instructions

The longer and more complex a prompt, the harder it is for a model to track every constraint simultaneously. Research and practical experience both show that instructions buried in the middle of a long prompt tend to be followed less reliably than those near the beginning or end — a phenomenon sometimes called the “lost in the middle” effect. Instructions that conflict with each other, or that require counting (word limits, numbered lists) are also consistently under-followed.

Running a quick compliance check after every generation — especially for templated or regulated outputs — is the fastest way to catch these before sending.

How it works

The tool splits your prompt into sentences and flags any that contain imperative cue words — must, should, do not, never, always, only — plus explicit length or format constraints. Each becomes a checklist item. For instructions it can verify mechanically (a banned word, a required phrase, a word limit) it runs the check against your output and shows a verdict with the reason. Instructions it cannot judge automatically are still listed so your checklist stays complete. Everything runs locally in your browser.

What it can and cannot verify

  • Auto-checkable: negative constraints (“do not mention X”), positive requirements (“must include Y”), and numeric limits (“under 100 words”).
  • Manual only: subjective or stylistic instructions (“be concise”, “sound friendly”) — surfaced for you to judge.

Practical example

Suppose your prompt contains:

  • “Do not mention any competitor brands.”
  • “Must include a disclaimer at the end.”
  • “Keep the response under 150 words.”
  • “Always use a friendly, casual tone.”

The checker would auto-verify the first three: it searches for known competitor names (if you listed them), checks for the word “disclaimer,” and counts the output’s words. The fourth instruction — tone — goes on your manual review list because tone is subjective. The result is a checklist with three auto-verdicts and one prompt to read yourself, rather than re-reading both texts from scratch.

Tips

  • Write prompt instructions as clear, separate sentences so the extractor catches each one.
  • Treat every verdict as a prompt to look, not a final ruling — heuristics produce both false positives and false negatives.
  • Re-run after editing the prompt to confirm new constraints were actually picked up.
  • For high-stakes outputs (legal, compliance, regulated copy), pair this with a human sign-off on every instruction, especially the manual-only ones.
  • Place your most important constraints at the beginning and end of the prompt — not buried in the middle — to improve the model’s own compliance before you even run a check.