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Email Copywriting · chunkydotdev | DecimalAI

marketingby chunkydotdev

Email Copywriting

chunkydotdev/email-copywriting

Source chunkydotdev/email-skills ↗License MIT

Write emails people actually read.

SkillScore87Maintained

Automatic

Marketing & Content pack

Last verified 8/6/2026

What it changes

Passed 20 of 23 test cases with the skill, and 16 of 23 without it.

Without skill70%

With skill87%

Checks it passed that the model alone missed

Advises keeping total links to 5 or fewer
Keeps the length between 30 and 50 characters
Restricts all subject line options to between 30 and 50 characters long

and 1 more in the full report

4 fixed16 passed either way3 still failing0 broke

Pass-rate lift: +17 pp
Tokens: +260%
Agent turns: 0%
Response time: -15%

Model gemini-3.6-flashMeasured 8/6/2026v120 of 23 cases passed with skill

Tokens, turns and time describe resource use, not a dollar price.

Use this skill

Save it into your project's skills folder. Claude Code picks it up in its next session.

curl -fsSL --create-dirs -o .claude/skills/chunkydotdev-email-copywriting/SKILL.md https://app.decimal.ai/s/chunkydotdev-email-copywriting/SKILL.md

Want it pinned and updatable? pip install "decimalai>=0.15", then decimalai skills add chunkydotdev-email-copywriting, and start Claude Code with claude --plugin-dir "$(git rev-parse --show-toplevel)/.agents"

1 · One-time — install the CLI (docs ↗)

pip install "decimalai>=0.15"

2 · Get the skill — writes .agents/skills/chunkydotdev-email-copywriting/ and pins it in .decimal/skills.lock

decimalai skills add chunkydotdev-email-copywriting

No CLI? Get the same file — curl · raw file

curl -fsSL --create-dirs -o .claude/skills/chunkydotdev-email-copywriting/SKILL.md https://app.decimal.ai/s/chunkydotdev-email-copywriting/SKILL.md

Raw file: /s/chunkydotdev-email-copywriting/SKILL.md ↗ · machine-readable summary at /s/chunkydotdev-email-copywriting.json ↗

Safety checks: 3 of 3 passed

Code scan CleanIntent PassedContent Clean

See it in action

One of 4 test cases the skill fixed. Same model, same prompt, with and without the skill.

1 of 4

Prompt

Re-write the subject line 'Our new dashboard reporting feature is live' using a question format to improve open rates.

What was checked, without and with the skill
Checked	Without skill	With skill
Phrases the subject line as a question	Passed	Passed
Keeps the length between 30 and 50 characters	Missed	Passed

case-18 · gemini-3.6-flash · 8/6/2026 · answers are capped and redacted

What's inside

The instructions your model reads when the skill loads.

SKILL.md444 linessingle file

Email Copywriting

Write emails people actually read - subject lines that get opened, body copy that gets read, and CTAs that get clicked.

When to use this skill

Writing any email - transactional, marketing, cold outreach, onboarding, or notifications
Improving open rates, click-through rates, or reply rates
Drafting subject lines or preview text
Structuring email body copy for engagement
Writing calls to action that convert
Reviewing email copy for spam-trigger phrases or tone issues
Adapting email content for mobile readers
Deciding between plain text and HTML format

Related skills

spam-filter-avoidance - content patterns that trigger spam filters
template-design - HTML email templates that render everywhere
ab-testing - testing subject lines, content, and send times
onboarding-emails - welcome sequences and activation emails
email-sequences - drip campaigns and automated sequences
email-compliance - CAN-SPAM, GDPR, unsubscribe requirements

Subject lines

The subject line determines whether your email gets opened. Average open rates hover around 22% globally, and most of the variance comes from the subject line.

Length

Keep subject lines between 30 and 50 characters (roughly 5-9 words). Front-load the most important words - on mobile, anything past 35-40 characters gets cut off. The first 3-4 words need to carry the message on their own.

Good: Your API key expires Friday Bad: Important information regarding the upcoming expiration of your API key

Formulas that work

Question format - gets 21% higher open rates than statements because it engages curiosity:

Track record

Benchmark

20 / 23

test cases passed, vs 16 / 23 without

Adoption

Users: 0
Times used: 0

Safety and source details

SkillSafety

✓ 3 of 3 passed

Code scan15 of 15 checks clean

0 critical · 0 warning · 0 info — scanner v4 — 8/2/2026

View 15 scanner checks

live_secretremote_code_executionreverse_shelldata_exfiltrationssrf_metadataagent_snoopinganti_refusaldestructive_commandsobfuscated_unicodeunicode_homoglyphopaque_blobsuspicious_urltool_overreachtrigger_abuseprompt_injection_phrasing

IntentSafe

LLM judge · does the skill do what it claims

ContentClean

LLM judge · policy & harmful-content review

Source

Imported

chunkydotdev / email-skills

skills/content/email-copywriting/SKILL.md

View on GitHub ↗

License MITImported 8/2/2026Version v1

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