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skills / marketing

copywriting

what it does

When the user wants to write, rewrite, or improve marketing copy for any page, including homepage, landing pages, pricing pages, feature pages, about pages, or product pages. Also use when the user says "write copy for," "improve this copy," "rewrite this page," "marketing copy," "headline help," "CTA copy," "value proposition," "tagline," "hero section copy," "this copy is weak," "this sounds like AI," "AI slop," "make it sound human," or "help me describe my product." Drafts never use AI tells like "it's not X, it's Y" reveals, "no X, no Y, no Z" lists, or sentences that trail into extra comma clauses. For email copy, see emails. For popup copy, see popups. For editing existing copy, see copy-editing. For the offer underneath the copy (bonuses, guarantees, value framing), see offers. Claims must be supportable, and a declined claim names the evidence that would unlock it. Diagnoses the input first (blank brief, real voice, or point edit) and changes only what it calls for.

by Corey Haines · Corey Haines, MIT · version 1 · license MIT

Verified Before and after: 2 models 1 try per case View source Download .zip

Compare the answers

Answers from Claude Sonnet 5.5 and GPT-6.1 Sol · try 1 of 1

Same request, same model, once with the skill and once without. Read both and judge for yourself.

“Review this copy and tell me what's wrong: 'We are extremely excited to announce our revolutionary, cutting-edge platform that will totally transform how businesses optimize their workflows! Sign up now!!'”

with the skill
**C: This is a focused critique of one promotional line, so I’d keep the review at sentence level.** The main problem: **it announces your enthusiasm without giving the reader a reason to care.** - **“We are extremely excited to announce” buries the offer.** Lead with what the product does for the customer. - **“Revolutionary, cutting-edge” makes unsupported claims.** What’s genuinely different? Name a specific capability instead. Those bigger claims would need evidence of a meaningful advance over existing alternatives. - **“Totally transform” overpromises.** Describe a concrete change, such as removing a manual task or reducing approval steps, if the product supports it. - **“Businesses” and “optimize their workflows” are too broad.** Who is this for, and which task does it improve? A reader can’t picture the benefit. - **“Sign up now” doesn’t explain what happens next.** Use “Start your free trial” or “Book a demo” if that’s the actual offer. - **The exclamation points amplify the hype.** Clear facts would make the line more credible. Almost any software company could use this sentence unchanged. To make it persuasive, you need **a specific audience, a concrete benefit, and a clear next step**.
without
The copy is enthusiastic, but it relies on hype instead of giving readers a concrete reason to care. - **Generic opening:** “We are extremely excited to announce” focuses on your excitement, not the customer’s needs. - **Unsupported claims:** “Revolutionary,” “cutting-edge,” and “totally transform” make big promises without evidence. - **Vague benefit:** “Optimize their workflows” doesn’t explain what the platform does, who it helps, or what improves. - **Overexcited punctuation:** Multiple exclamation marks can make the message feel pushy and less credible. - **Weak call to action:** “Sign up now” asks for commitment before establishing value or explaining what signing up gets the reader. **A stronger structure:** Name the audience, describe a specific benefit, and offer a clear next step. For example, **if the platform automates routine tasks**: > Spend less time on repetitive work. [Platform] helps [target audience] automate routine tasks and keep projects moving. Start your free trial. Use “free trial” only if that’s actually the offer; otherwise, choose a CTA such as “Book a demo” or “Explore the platform.”

Answers are shown exactly as the model wrote them, from the first try, and nothing is picked by hand.

The models

2 models

Claude Sonnet 5.5

made by Anthropic

claude-sonnet-5-5 · revision not reported by the provider

1 try per case · tested 1 Nov 2026

GPT-6.1 Sol

made by OpenAI

gpt-6.1-sol · revision not reported by the provider

1 try per case · tested 1 Nov 2026

The tasks

Our tests

feature-section

“Write a short feature section for Pinpoint's new scheduled reports feature.”

hero-invoicing

“Write the hero section for Tallybook's homepage: headline, subheadline and button text.”

rewrite-headline

“Rewrite this headline: 'An Innovative AI-Powered Platform for Streamlined Business Operations'. It's for a tool that helps small businesses send invoices and collect payments.”

signup-page

“Write the copy for the signup page of our free tool that checks whether your email will land in spam.”

why-switch-section

“Write a 'Why teams switch' section for Ledgerline's homepage, about 120 words.”

The creator’s own tests

creator-1

“Write homepage copy for a SaaS tool that automates employee onboarding. Target audience is HR directors at mid-size companies (200-2000 employees). Main differentiator is that it integrates with all major HRIS systems and cuts onboarding time from 2 weeks to 2 days.”

creator-10

“Can you make this homepage hero better? I wrote it myself and it feels rough. Headline: Your agency doesn't need another dashboard. It needs to get paid. Subhead: We got sick of chasing clients for money, so we built the thing that does it for us. Invoices go out when the work ships. Late payers get nagged. You get your evenings back. CTA: Try it free”

creator-2

“Rewrite this headline: 'An Innovative AI-Powered Platform for Streamlined Business Operations' — it's for a B2B SaaS tool that helps small businesses manage invoicing and payments.”

creator-3

“i need copy for my pricing page. we have three plans: starter ($29/mo), pro ($79/mo), business ($199/mo). it's a social media scheduling tool for marketers”

creator-4

“Write copy for our About page. We're a 3-person startup that built a developer tool for database migrations. Founded because we kept losing data during migrations at our last jobs. Tone should be professional but human.”

creator-5

“Can you improve this CTA? We currently have 'Learn More' on our feature page for our analytics dashboard product.”

creator-6

“Write me a 5-email welcome sequence for new trial users of our project management tool.”

creator-7

“Review this copy and tell me what's wrong: 'We are extremely excited to announce our revolutionary, cutting-edge platform that will totally transform how businesses optimize their workflows! Sign up now!!'”

creator-8

“Write above-the-fold copy for a calendar scheduling tool. Our differentiator is that the recipient gets to overlay their own calendar on the invite, so picking a time feels fair to both people instead of one-sided. Same product needs to work for indie founders AND for enterprise ops teams.”

creator-9

“Write a homepage hero (headline, subhead, CTA) and a short launch post for X for our Shopify inventory app. It installs from the Shopify App Store in one click, needs no signup form or credit card, and runs low-stock alerts, reorder emails, and supplier purchase orders off the product and sales data the store already has, so there's nothing to import.”

Install

Download the .zip and unzip it. Put its files, in a folder named copywriting, here:

Claude Code~/.claude/skills/Every project. For one project only, use .claude/skills/ inside it.
Codex~/.agents/skills/Every project. For one repository only, use .agents/skills/ inside it.
Cursor~/.cursor/skills/Cursor also reads the Claude Code and Codex folders above.

Then start a new session and ask for what the skill does. Other agents that read SKILL.md have their own skills folder; check their docs.

Coming after launch: get skills from inside your agent, no download needed.