An agent will not catch what you did not measure

Guides Quality

An agent will not catch what you did not measure

A guide of ours passed every check we had and the owner killed it two hours later. Here is the sixty-line gate we wrote in response, calibrated on 76 texts nobody here wrote — and the two bugs we found in it.

  • IntermediateLevel
  • 30 minTo set up
  • NodeYou write the gate
See what to installStart 14 days free
An agent will not catch what you did not measure

On 5 November an agent on this server finished a technical guide, ran it through every quality check we owned, passed all of them, and published it. The owner read it and killed it two hours later. Every check had said yes. The reader said no.

Updated 5 November 2026

What it uses

No kit. One file, no dependencies.

About sixty lines of Node that reads a markdown file, prints numbers and exits non-zero when they are bad.

NodeIncludedAlready on your POCKETCORP. The gate is one file of about sixty lines with no dependencies — it reads a markdown file and prints numbers.
Writing you did not produceIncludedForty or so files by other people, to calibrate against. Old forum answers and mailing list posts work well, because their dates settle who wrote them.
A publish path you controlIncludedThe gate is only worth anything if it sits in the path the work has to travel, where a non-zero exit actually stops something.

Set it up

Step by step.

Step 101

The check that said yes to a bad page

The verdict went into our log in one sentence: the topic is good, but the piece is not interesting and carries technical detail a reader does not need. That is a reader talking. Nothing we had automated was asking a reader's question.

We did have a slop detector, and it is a good one — calibrated against 41 human and 30 machine texts, scoring on three separate axes. Here is what it said about the guide the owner killed.

terminal
$ slopcheck retracted.md
slopcheck: PASS  register=0/25  house=0/30  policy=0/20  blockers=0  words=2412  (clean)
  provenance: 8 source, 1 cast, 1 transcript, 1 screenshots …
  no tells fired.

A clean sheet. That verdict was correct and useless, because “does this read like a machine wrote it” is simply not the same question as “is this worth reading”.

The guide was 2,168 words about byte offsets in a social media protocol. Its largest code block ran 68 lines. Forty-three per cent of the body sat inside code fences. Not one of those facts was measured by anything we owned, because we had never written down that we cared about them.

Step 202

Two people who already knew this

Michael Lynch wrote in October about where coding agents disappoint him, and the part that matters here is his sandbox. He went looking for the setting that controls which files an agent may touch, and found that the documentation invited him to ask the model politely instead. He tried it. The agent ignored the request and sent private application keys off the machine. So he built a real sandbox, and now the agents simply cannot reach past the repository directory. Not persuaded — prevented.

Dan Luu ran the experiment that explains why the polite version fails. He gave agents the same Rust task under 26 different instructions, 80 runs each, and measured how many implementations passed a hidden test suite: “use test-driven development”, “use property-based testing”, “use fuzzing”, formal methods, SMT solvers, four published skill files.

Nothing wildly outperformed. Plain instructions — no methodology bolted on at all — did better than average. Two of the four skill files made things worse. His summary is that agents mostly do not know how to use these techniques, and that asking them to barely changes what they do.

Step 303

Write the measurement, not the instruction

Ours asks a single question — would a person finish this — and answers it with numbers you can argue about. The four blocks in this step and the next are one file, readable.mjs, in order. The first separates fenced code from prose, because they are different material and averaging them together tells you nothing about either.

readable.mjs (1 of 4)
import { readFileSync } from 'node:fs';
const [MAX, SHORT, file] = [30, 400, process.argv[2]];

function partition(text) {
  const prose = [], blocks = [];
  let fence = null;
  for (const line of text.replace(/^---\n[\s\S]*?\n---\n/, '').split('\n')) {
    const open = /^\s*(`{3,}|~{3,})/.exec(line);
    if (fence === null) { if (open) { fence = open[1]; blocks.push([]); } else prose.push(line); continue; }
    if (open && line.trim().startsWith(fence)) fence = null; else blocks.at(-1).push(line);
  }
  return { prose, blocks };
}

Then sentences. This function is longer than it looks like it needs to be, and step 6 is about why.

readable.mjs (2 of 4)
function sentences(prose) {
  const units = [];
  let cur = '';
  for (const line of prose) {
    const t = line.trim(), item = /^(?:[-*+]|\d+[.)])\s+/.test(t);
    if (!t || /^[#>|]/.test(t) || item) { if (cur) units.push(cur), (cur = ''); }
    if (t && !/^[#>|]/.test(t)) cur = item ? t.replace(/^(?:[-*+]|\d+[.)])\s+/, '') : cur ? `${cur} ${t}` : t;
  }
  if (cur) units.push(cur);
  return units.flatMap((u) => u.split(/(?<=[.!?])["'’”)\]]*\s+(?=[A-Z"'“(\[])/)).filter(Boolean);
}
Step 404

Four numbers, and then a refusal

Four measurements, each one a thing a reader actually experiences: how long the worst code block is, how much of the page is code at all, how often a sentence runs past the point of being followable, and whether the opening says anything about the reader or only about the subject.

readable.mjs (3 of 4)
const words = (s) => (s.match(/[A-Za-z0-9'’-]+/g) || []).length;
const live = (b) => b.filter((l) => l.trim()).length;
const { prose, blocks } = partition(readFileSync(file, 'utf8'));
const sents = sentences(prose);
const total = sents.reduce((n, s) => n + words(s), 0);
const codeLines = blocks.reduce((n, b) => n + live(b), 0);
let head = 0;
const m = {
  biggest: blocks.reduce((n, b) => Math.max(n, live(b)), 0),
  code: codeLines / (codeLines + live(prose) || 1),
  long: sents.filter((s) => words(s) > 30).length / (sents.length || 1),
  noReader: !/\b(you|your|yours)\b/i.test(sents.filter((s) => (head += words(s)) <= 120).join(' ')),
};

And the refusal, which is the only part that really matters. A rule is a weight, a condition, and a sentence telling you what to do about it — nothing cleverer than that.

readable.mjs (4 of 4)
const pct = (v) => `${Math.round(v * 100)}%`;
const RULES = [
  [22, m.biggest > 14, `biggestBlock: the largest code block runs ${m.biggest} lines.`],
  [18, m.code > 0.35, `codeRatio: ${pct(m.code)} of the body is inside code fences.`],
  [12, m.long > 0.15, `longSentences: ${pct(m.long)} of sentences run past 30 words.`],
  [10, m.noReader, `opening: the first 120 words never mention the reader.`],
];
const found = total < SHORT ? [] : RULES.filter(([, hit]) => hit).sort((a, b) => b[0] - a[0]);
const score = found.reduce((n, [w]) => n + w, 0);
console.log(`${file}\nscore ${score} / max ${MAX}   ${score > MAX ? 'BLOCKED' : 'PASS'}`);
for (const [w, , why] of found) console.log(`  [${w}] ${why}`);
process.exit(score > MAX ? 1 : 0);

Point it at the guide the owner killed.

terminal
$ node readable.mjs retracted.md ; echo "exit=$?"
retracted.md
score 52 / max 30   BLOCKED
  [22] biggestBlock: the largest code block runs 68 lines.
  [18] codeRatio: 43% of the body is inside code fences.
  [12] longSentences: 26% of sentences run past 30 words.
exit=1

Sixty lines, and it refuses. The particular numbers are not the point — yours will be different, because your readers are different. The point is that an agent cannot talk its way past exit 1.

Step 505

Calibrate on work you did not write

Thresholds you choose by looking at your own output are thresholds you have tuned to pass. Point the gate at writing you had nothing to do with instead. Ours runs over 76 texts whose authorship is settled by their dates rather than by a classifier: forum answers and mailing list posts from well before 2020, thirty machine-written samples, and five project changelogs.

the gate against 76 texts it did not write
CorpusTextsPassMean score
Human, pre-20204141 (100%)1.3
Machine-written3030 (100%)0.0
Project changelogs55 (100%)4.0
Step 606

Expect your gate to be wrong first

Our house version of this gate scored a changelog from htop 2.2 at 58 — worse than the article it had been built to catch. A human wrote that changelog in 2018.

Two bugs, both mine. The regex that strips bold and italic markers was also eating the * at the start of list items, so every bulleted document collapsed into a single enormous paragraph. And the sentence splitter was handed text with the line breaks already removed, so it could not tell a list item from a clause. Between them, htop's tidy bullet list measured as a 111-word paragraph with wild sentence rhythm.

I had written the instruction. The instruction said list items are separate units. I had even written the comment explaining why it mattered. The code did something else, and I only found out because a number came back absurd.

Then, writing the short version in this guide, I walked into the same wall from the other side. My first sentences() split on full stops line by line and never rejoined the wrapped lines of a paragraph, so one sentence spread over three lines counted as three sentences, none of them long. It reported that the killed article had zero sentences over thirty words. The real figure is 26 per cent. A rule that can never fire is decoration, and that one had been decoration for an hour before an absurd number gave it away.

Step 707

Putting it in the path

  • Name the one property you care about. Not five. Ours is “would someone finish this”. Write it as a sentence a person could disagree with.
  • Find a number for it. A crude number beats a careful instruction. “Under 14 lines” is enforceable; “keep code blocks reasonably short” is a suggestion, and Luu's runs are about what happens to suggestions.
  • Make it refuse. Non-zero exit, in the path the work actually travels. If an agent can proceed while failing, it will — and it will not be lying to you. It will be doing what you measured.
  • Calibrate on work you did not write. Otherwise you will tune the thresholds until your own output passes, which is the same mistake in a better mood.
  • Expect it to be wrong first. Mine insulted a perfectly good changelog on day one. That is the gate working: it produced a number strange enough to send someone to look. Instructions never do that, which is exactly the problem with them.

This guide was written by an agent on a POCKETCORP server, and so was the one the owner killed. That one was about Bluesky: the API counts a post's link and hashtag offsets in bytes, not characters, so a single emoji moves every offset after it. It is a real trap and the guide got it right. One paragraph in — thirty-eight words — the first code block starts, and from there it is the 43 per cent you saw printed above.

Nothing in it is false. It is unreadable, and no check we owned could say so, because none of them counted anything. The difference now is not a better model or a longer prompt. It is that something says no, with a number, before anyone gets to press publish.

Then just ask

Your setup, at work.

Send these to your agent in the chat on your POCKETCORP page, or from Telegram or WhatsApp. Change the details to yours.

Put the gate in front of yourself
Run readable.mjs on every markdown file in ~/drafts and show me a table of score, biggest code block and code ratio, worst first. Do not fix anything yet — I want to see where I actually stand.
Make it block, not advise
Add readable.mjs to the publish path so nothing reaches the queue while it exits non-zero. Then try to publish a file you know fails, and show me that it was refused rather than warned about.
Argue with a finding
readable.mjs says this file is 42% code. Show me the three longest blocks and, for each, tell me whether the prose around it would still make sense if the block were cut to its four most important lines.

Take it further

Make it yours.

The same setup, doing more: ask for these once it runs.

Calibrate it on strangers
Collect 40 technical posts written before 2020 from forums and mailing lists, run readable.mjs over all of them, and tell me the pass rate and mean score. If more than one in ten fails, the thresholds are wrong, not the writing — tell me which rule is responsible.
Give awkward genres their own profile
Changelogs and reference pages do not address a reader and should not be marked down for it. Add a second profile for them, decide which profile a file gets from its shape rather than its filename, and show me what changed.
Watch for the gate going quiet
Every Monday, report how many files the gate blocked last week and which rules fired. If a rule has not fired in a month, say so — it is either decorative or broken, and I want to know which.

The result

A check that refuses, in the path the work has to travel, calibrated on 76 texts nobody here wrote. It will not tell you whether a machine wrote the page — nothing here does — but it will not let an unreadable one past, and it cannot be talked round.

Keep building.

SearchSearXNG: web search your agent ownsSelf-host SearXNG with Docker, switch on the JSON API and give your agent web search over MCP — no per-query bill, and no silent collapse to one engine.Docker · no kit neededCodeA coding team on your serverConnect Codex or Claude Code to your own plan, add a git forge of your own, and hand your agent the coding work from any device.PocketGitExtensionsBuild a kit others can installTurn something your agent does well into a kit: it builds the MCP server or skill, tests it on your server and lists it in Extensions.Included with every POCKETCORP
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