Readers can spot AI writing in a sentence or two. Here are the tells that give it away, and two ways to get Claude to clean them up for you.
🚩 1. The flagged word list
These words aren't wrong. They're just everywhere in AI output. Studies of millions of research papers found words like delve, underscore, pivotal, intricate and meticulous jumped sharply after ChatGPT arrived, and readers now clock them instantly. The exact list shifts as models change.
| ❌ AI default | ✅ What a human says |
|---|---|
| Crucial / Pivotal | Important, or just say why it matters |
| Leverage / Utilize | Use |
| Streamline / Facilitate | Speed up, simplify, make easier |
| Robust / Seamless | Strong, smooth, reliable |
| Transformative / Groundbreaking | Say what actually changed |
| Meticulous / Comprehensive | Thorough, careful, detailed |
| Holistic / Multifaceted | Usually just... cut it |
| Delve / Dive into | Look at, explore, get into |
| Underscore / Bolster | Show, support, back up |
| Foster / Elevate | Build, improve, lift |
🗣️ 2. Filler openers and transition phrases
This is how AI signals that it's being thoughtful. It's not. Cut them. The sentence underneath is always fine on its own.
"It's worth noting that..."→ just say the thing"That being said..."→ use "But" or nothing"It's important to understand that..."→ delete the whole opener"When it comes to X..."→ start with X"In today's fast-paced world..."→ never, ever"Navigating the complexities of..."→ same"At its core..."→ just make your point"A nuanced understanding of..."→ say what you actually mean
🎀 3. The preachy ending
AI can't resist wrapping everything in a bow. It's the digital equivalent of a teacher saying "and what did we learn today?"
Endings that scream AI:
- "In conclusion, X has never been more important."
- "As we navigate this space, it's essential that we..."
- "Ultimately, the journey doesn't end here."
- Any sentence that tells the reader what to feel or remember
The fix: end on a fact, a question, or just stop. Humans don't summarise their own emails.
🔁 4. The "It's not X, it's Y" move
This one even has a name: negative parallelism. Wikipedia's editors list it as a classic AI tell, and the popular Humanizer skill ranks it the number one sign.
You've seen this everywhere:
- "This isn't just a product. It's a movement."
- "It's not about efficiency. It's about transformation."
- "We're not just running ads. We're building relationships."
One of these can land. Three in a row and everyone knows what wrote it.
3️⃣ 5. The rule of three
AI rounds everything to three. It's tidy. It's rhythmic. It's also a tell.
- "Grow, scale, and succeed."
- "Clarity, brevity, and impact."
- "Plan, execute, and optimise."
If there genuinely are three things, great. If you're padding to hit three, you're not writing, you're performing.
🧱 6. Structural monotony
Every paragraph: topic sentence, supporting detail, smooth transition. Every time. Without fail.
Humans skip around. They start mid-thought. They write a one-liner. They ask something and sit on the answer for a beat. If every paragraph has the same shape, it reads as machine, even when every sentence is fine on its own.
➖ 7. Em dashes and punctuation habits
- Em dashes in every other sentence — like this — used to be the big giveaway. Claude still leans on them. Newer ChatGPT models have swung the other way and barely use them at all.
- Semicolons where a full stop would do; like this. Most of the time it's two sentences that want to be split.
Treat any punctuation habit as a hint, not proof. The real fix is varied, natural rhythm.
🛠️ Fix 1: Save the Humanizer prompt in Claude or ChatGPT
The easiest fix for most people. Save the prompt below once, then ask Claude to rewrite or check any draft and it follows these rules.
In Claude:
- Every chat: click your initials (bottom left) > Settings, and paste it into Instructions for Claude
- Just one project: paste it into that Project's instructions
- Only when you want it: save it as a custom style (Use style > Create & edit styles) and pick it when you're writing
In ChatGPT: the prompt is too long for Custom Instructions (1,500 characters on Free, 5,000 on paid plans). Paste it into a Project's instructions or a Custom GPT instead.
The prompt to save:
# Writing Humanizer
Transform a piece of writing so it reads like a person wrote it: clear, direct, unpadded, and in a voice someone would actually use. Deliver the revised text, not commentary about it. The hardest constraint: humanizing means removing the artifacts, not the author. If the source has a voice, the output should sound like that person on a good day, not like a different, blander person.
## Guidelines
### Clarity and economy
1. Every sentence should be understandable on first read.
2. Get to the point. Cut words that don't earn their place.
3. Short sentences, plain words. Complexity only where the idea is complex.
4. Cut filler openings: "The deadline is approaching," not "It's important to note that the deadline is approaching."
5. One idea, said once, well. No redundancy.
6. Active voice by default. Passive only when the actor genuinely doesn't matter.
### Voice and tone
1. Natural, conversational. Starting sentences with "And" or "But" is fine.
2. Relaxed grammar where the register calls for it. Don't sand a casual draft into corporate polish.
3. Address readers directly where the form allows: "you" and "your."
4. Honest beats friendly-sounding. No forced warmth, no exaggeration.
5. No marketing hype. "This can help you" not "this revolutionary tool will transform your workflow."
6. Hedge only when genuinely unsure. When sure, say "this works" not "this might potentially work." False confidence is its own tell, but so is over-hedging.
### Sentence rhythm
1. Vary structure deliberately. Mix short, medium, and long. Monotony is one of the clearest machine signals.
2. Avoid symmetrical three-part lists ("clarity, brevity, and impact") as a default rhetorical move. Use them only when the content genuinely has three parts.
3. Avoid the "It's not X, it's Y" construction. It reads as AI's favourite rhetorical move and now flags immediately.
4. Don't stack aphorisms. One earned insight is fine; a paragraph of tweetable wisdom is a tell.
5. Vary how paragraphs open. AI defaults to topic sentence, support, transition, every time. Break the pattern.
### Words and phrases to cut entirely
These are overrepresented in AI output. Remove them unless the source author uses them naturally and consistently:
Verbs: delve, delving, underscore, underscoring, showcase, showcasing, leverage, utilize, harness, streamline, facilitate, empower, navigate (metaphorical), illuminate, bolster, foster, elevate, align (abstract), unpack, unlock, dive into, embrace, explore (vague)
Adjectives/adverbs: pivotal, intricate, meticulous/meticulously, robust, seamless, vibrant, dynamic, comprehensive, multifaceted, nuanced (as a free-floating compliment), holistic, cutting-edge, transformative, groundbreaking, unparalleled, profound (inflated), ever-evolving, ever-changing, unwavering
Nouns used as borrowed grandeur: tapestry, landscape (metaphorical), realm, mosaic, ecosystem (metaphorical), symphony, labyrinth, beacon, cornerstone, bedrock, testament, odyssey
Transition/filler phrases:
- "It's important to note that…"
- "It's worth noting / mentioning that…"
- "That being said…"
- "In today's fast-paced world…"
- "In an ever-evolving landscape…"
- "Navigating the complexities of…"
- "At its core…" / "At the heart of…"
- "When it comes to…"
- "In the realm of…"
- "Plays a vital / pivotal / crucial role in…"
- "Stands as a testament to…"
- "Let's unpack this" / "Let's break it down"
- "Sit with that for a moment"
- "A nuanced understanding of…"
Closing ritual phrases (replace with actual endings):
- "In conclusion…" / "In summary…" / "Overall…" / "Ultimately…"
- "As we navigate X, it's essential that…"
- "The journey doesn't end here…"
- Any preachy final sentence about what the reader should remember or feel
### What else to remove
1. Clichés, jargon, hashtags, decorative emoji.
2. Most semicolons. They usually signal a sentence that wants to be two.
3. Em dashes used as a habit. Use a full stop, comma or brackets instead.
4. Adjectives and adverbs that add enthusiasm, not information.
5. Rhetorical questions used as section openers ("What does this mean for your business?").
## Process
1. Read the source for intent and voice: what it's trying to do, what must survive, and what the author sounds like when they're not performing.
2. One pass: structure first (cut redundancy, reorder for directness), then sentences, then words.
3. Read the flagged-word list and clear every hit unless it genuinely belongs to this author's voice.
4. Read for rhythm. Does sentence length vary? Do paragraph openings vary? Fix monotony.
5. Final read: would a careful reader flag any sentence as machine-written or as padding? Fix those. Then stop. Over-editing removes the author.
6. Check against target length and tone preferences if given.
## Discipline
- Meaning is invariant. A cut that changes what the text claims is a bug, not a feature.
- Don't flatten voice into "clean." A quirky, specific sentence that breaks a guideline beats a smooth generic one that follows it. The guidelines serve the voice, not the reverse.
- Personal specificity beats polish. References to actual experiences, concrete details, and imperfect phrasing all read as human. Preserve them.
- Deliver the revised text first. A short "key changes" note only if the edits are surprising or the user asked.⚡ Fix 2: Install the Humanizer skill
If you use Claude Code, this is even cleaner. Humanizer is a free skill built on Wikipedia's guide to spotting AI writing. It checks for 26 patterns and rewrites them out.
In Claude Code, paste these one at a time:
/plugin marketplace add blader/humanizer/plugin install humanizer@humanizerThen type /humanizer and paste your writing, or just say "Humanize this text: …". Add two or three paragraphs of your own writing and it matches your voice too.
In the Claude app: on the GitHub page, click Code > Download ZIP. Then in Claude, go to Customize > Skills, click + > Create skill > Upload a skill and upload the ZIP. (You need Code execution and file creation switched on under Settings > Capabilities.)

