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.

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.

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

Source material given with the request

Tool: Inboxcheck. You send one test email to an address we give you; within 2 minutes you get a report on spam-filter results at Gmail, Outlook and Yahoo, plus SPF, DKIM and DMARC setup. Free, 3 checks per day, email address required.
with the skill
**Diagnosis: A.** The brief is a product description with no existing copy or voice, so I built the argument from the facts you gave. I added no stats, customers or claims beyond them. Open items are marked `[NEED]`. --- ## Page copy **Headline** Send one test email. See in 2 minutes whether it lands in spam. **Subhead** We give you an address to send to. You get back your spam-filter results at Gmail, Outlook and Yahoo, plus your SPF, DKIM and DMARC setup. **Form** Field label: Your email address Button: **Get my test address** Microcopy under button: Free. 3 checks per day. Microcopy under field: `[NEED: what the email is used for (login, report delivery, product updates?) and whether it's added to a mailing list. One honest line here will lift completion.]` ---
Show the rest (70 more lines)
**Section: How it works** 1. **Sign up with your email.** You get a test address right away. `[NEED: confirm the address appears immediately after signup, with no confirmation email first]` 2. **Send one email to it.** Use the same account or domain you send real email from, so the report reflects your real setup. 3. **Read your report.** It arrives within 2 minutes. --- **Section: What's in the report** *Spam-filter results at Gmail, Outlook and Yahoo* See how each of the three providers treated your email. *SPF* Checks that the servers sending your email are ones your domain has approved. *DKIM* Checks that your email carries a valid signature proving it wasn't altered in transit. *DMARC* Checks that your domain tells receiving servers what to do when SPF or DKIM fail. `[NEED: does the report give pass/fail only, or also say what to change? If it includes fix instructions, add a line here. It's a strong selling point.]` --- **Section: FAQ** **What does it cost?** Nothing. Each account gets 3 checks per day. **How long does a check take?** You get your report within 2 minutes of sending the test email. **Which inboxes do you test?** Gmail, Outlook and Yahoo. **Why do you need my email address?** `[NEED: real answer]` --- **Final CTA** Heading: Run your first check now Button: **Get my test address** Microcopy: Free. 3 checks per day. --- ## Annotations - **Headline:** It leads with the mechanism (one email, 2 minutes), the two facts that make the tool feel low-effort. It passes the "Now you can" test: now you can see whether your email lands in spam in 2 minutes. - **Subhead:** It names the three providers and three protocols because those are your differentiators. Someone searching for a spam checker will look for those words. - **Acronym explainers:** Your audience likely includes marketers and founders who know the terms exist but not what they do. Each is one plain sentence. - **Limits are stated up front:** "3 checks per day" sits next to the button so nobody finds the cap after signing up. - **Sparse by design:** I didn't add testimonials, logos or a comparison section, since you've given me no proof to fill them. ## Headline alternatives - **B:** See how Gmail, Outlook and Yahoo treat your email. *Rationale: names the providers, which is the most concrete part of the report. Less urgency than the main headline.* - **C:** Find out if your email goes to spam before your customers do. *Rationale: stronger pain, but implies you check before sending to a list, which depends on how people use the tool.* ## Meta - **Title:** Inboxcheck: Free Email Spam Test for Gmail, Outlook and Yahoo - **Description:** Send one test email and get spam-filter results at Gmail, Outlook and Yahoo, plus your SPF, DKIM and DMARC setup, in 2 minutes. Free, 3 checks per day. ## What I need from you 1. **Why the email address is required.** Without it, the field invites suspicion. Whatever the answer is, say it plainly. 2. **Whether the report includes fixes.** I can't claim it does without confirmation. 3. **Proof, if you have any.** Examples are a count of checks run, a named user quote, or a sample report screenshot. A sample report is probably the strongest addition, and I'd place it right under the hero.
without
# Inboxcheck signup page copy ## Hero **Headline:** Will your email land in spam? Find out in 2 minutes. **Subhead:** Send one test email. Get a report on how Gmail, Outlook, and Yahoo treat it, plus a check of your SPF, DKIM, and DMARC setup. **Primary CTA button:** Get my free test address **Under the button:** Free. 3 checks per day. Just your email address to start. --- ## Signup form **Form label:** Your email address **Placeholder:** you@company.com
Show the rest (65 more lines)
**Button:** Get my free test address **Helper text:** We'll send your report here and use this address to track your 3 daily checks. --- ## How it works **1. Get your test address** Enter your email and we'll give you a unique address to send to. **2. Send us a test email** Send it from the account or tool you actually use for sending, so the results reflect reality. **3. Read your report** Within 2 minutes, you'll see where your email landed and what to fix. --- ## What you'll see in your report **Spam-filter results at the big three** See how Gmail, Outlook, and Yahoo handle your message. **SPF, DKIM, and DMARC checks** Find out whether your authentication is set up correctly, so you can fix problems before they cost you replies. --- ## Who it's for Anyone who sends email and needs it to be read: founders sending outreach, marketers launching campaigns, developers setting up a new domain or sending service. --- ## FAQ **Is it really free?** Yes. You get 3 checks per day at no cost. **What do I need to sign up?** Just your email address. **How long does a check take?** Your report is ready within 2 minutes of sending your test email. **Which inboxes do you test?** Gmail, Outlook, and Yahoo. **What are SPF, DKIM, and DMARC?** They're the authentication records that prove your email really comes from you. Missing or misconfigured records are a common reason email gets filtered as spam. Your report shows whether each one is set up correctly. --- ## Closing CTA **Headline:** Don't guess where your email is landing. **Button:** Run my free check --- ### Notes - I didn't add claims like "no credit card required" or "no spam from us" since they weren't in your brief. Add them if they're true, as they'd help conversion near the button. - If you have a sample report, a screenshot placed beside "What you'll see in your report" would do more than any copy there.

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.