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subject-line-lab

subject-line-lab is a skill for Claude Code from cognyai/claude-code-marketing-skills. It costs 60 tokens per session (5,960 once invoked), scanned A, original, no licence file.

A tool that studies your past email subject lines from Klaviyo, Mailchimp, Rule, or Get a Newsletter. It finds patterns in your own mailing-list history and generates new subject-line candidates from them.

In plain words
What is it for?
It helps review subject-line history, identify recurring patterns, and draft candidates tuned to an email list.
Why use it?
It helps replace generic subject-line advice with ideas based on what has worked for your specific audience.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter.

not rated 114repo +2 changed 25d ago A scan 60 tokens no licence

Good fit It helps review subject-line history, identify recurring patterns, and draft candidates tuned to an email list.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/cognyai/claude-code-marketing-skills/subject-line-lab
View source ↗ cognyai/claude-code-marketing-skills cogny.com
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add cognyai/claude-code-marketing-skills --skill subject-line-lab
Clone the repo
git clone --depth 1 https://github.com/cognyai/claude-code-marketing-skills

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for subject-line-lab

README.md
[![agentmods](https://agentmods.dev/badge/skills/cognyai/claude-code-marketing-skills/subject-line-lab/github.svg)](https://agentmods.dev/skills/cognyai/claude-code-marketing-skills/subject-line-lab)
Your own site
<a href="https://agentmods.dev/skills/cognyai/claude-code-marketing-skills/subject-line-lab"><img src="https://agentmods.dev/badge/skills/cognyai/claude-code-marketing-skills/subject-line-lab/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for subject-line-lab

Your own site · 80×15
<a href="https://agentmods.dev/skills/cognyai/claude-code-marketing-skills/subject-line-lab"><img src="https://agentmods.dev/badge/skills/cognyai/claude-code-marketing-skills/subject-line-lab.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 60 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 5,960 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin unknown No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00060 $0.05960
Opus 5.5 $0.00024 $0.02384
Sonnet 5.5 $0.00012 $0.01192
Haiku 4.5 $0.00006 $0.00596

Measured 25d ago against content hash b3519c154dfa, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

subject-line-lab scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 25d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/subject-line-lab/SKILL.md · 337 lines

The source is not reproduced here

No licence file

A repository with no LICENSE is all rights reserved by default, so the body is not copied here. The metadata, the measurements and the link are.

Read it on GitHub

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 25d ago Changed · +133 lines · +22 tokens per session b3519c154dfa
  2. 2mo ago First seen · 204 lines · 38 tokens per session scan A d6ff778c5d05

Subscribe to this mod's changes

subject-line-lab is a skill published in the GitHub repository cognyai/claude-code-marketing-skills (114 stars, last pushed 25d ago), with no licence file. It adds 60 tokens to every session and 5,960 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

Analytics and metricsClaude CodeMarketing and SEOagent-skillsai-agentsclaude-skillscluade-mcpcursor
Related

subject-line-lab compared with skills from other repositories

subject-line-lab next to 6 skills from other repositories
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