Email Marketing Bible
CosmoBlk/email-marketing-bible
Email marketing operating manual for AI agents, with hard send-safety gates.
Mine your actual subject-line history from Klaviyo / Mailchimp / Rule / Get a Newsletter, find the patterns that work for YOUR list, and generate tuned candidates
Install Subject Line Lab
$ npx skills add cognyai/claude-code-marketing-skills --skill subject-line-lab -a claude-codeProject install by default; add -g for ~/.claude/skills/.
$ gh skill install cognyai/claude-code-marketing-skills subject-line-lab --agent claude-codeProject scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).
$ git clone --depth 1 https://github.com/cognyai/claude-code-marketing-skills.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/subject-line-lab .claude/skills/subject-line-lab && rm -rf skills-srcUse ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.
Claude Code skills documentation · loads skills from .claude/skills/
Install the "subject-line-lab" agent skill from https://github.com/cognyai/claude-code-marketing-skills/tree/main/skills/subject-line-lab into .claude/skills/subject-line-lab/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "subject-line-lab", then confirm the skill loads.Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$skill-installer install https://github.com/cognyai/claude-code-marketing-skills/tree/main/skills/subject-line-labType this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.
$ npx skills add cognyai/claude-code-marketing-skills --skill subject-line-lab -a codexProject install goes to .agents/skills/; add -g for ~/.codex/skills/.
$ gh skill install cognyai/claude-code-marketing-skills subject-line-lab --agent codexProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/cognyai/claude-code-marketing-skills.git skills-src && mkdir -p .agents/skills && cp -r skills-src/skills/subject-line-lab .agents/skills/subject-line-lab && rm -rf skills-srcUse ~/.agents/skills/ instead of .agents/skills for a personal install.
Codex skills documentation · loads skills from .agents/skills/
Install the "subject-line-lab" agent skill from https://github.com/cognyai/claude-code-marketing-skills/tree/main/skills/subject-line-lab into .agents/skills/subject-line-lab/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "subject-line-lab", then confirm the skill loads.Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add cognyai/claude-code-marketing-skills --skill subject-line-lab -a cursorProject install goes to .agents/skills/; add -g for ~/.cursor/skills/.
$ gh skill install cognyai/claude-code-marketing-skills subject-line-lab --agent cursorProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/cognyai/claude-code-marketing-skills.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/skills/subject-line-lab .cursor/skills/subject-line-lab && rm -rf skills-srcUse ~/.cursor/skills/ instead of .cursor/skills for a personal install.
Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/
Install the "subject-line-lab" agent skill from https://github.com/cognyai/claude-code-marketing-skills/tree/main/skills/subject-line-lab into .cursor/skills/subject-line-lab/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "subject-line-lab", then confirm the skill loads.Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gemini skills install https://github.com/cognyai/claude-code-marketing-skills.git --path skills/subject-line-lab--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.
$ npx skills add cognyai/claude-code-marketing-skills --skill subject-line-lab -a gemini-cliProject install goes to .agents/skills/; add -g for ~/.gemini/skills/.
$ gh skill install cognyai/claude-code-marketing-skills subject-line-lab --agent gemini-cliProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/cognyai/claude-code-marketing-skills.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/skills/subject-line-lab .gemini/skills/subject-line-lab && rm -rf skills-srcUse ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.
Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/
Install the "subject-line-lab" agent skill from https://github.com/cognyai/claude-code-marketing-skills/tree/main/skills/subject-line-lab into .gemini/skills/subject-line-lab/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "subject-line-lab", then confirm the skill loads.Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gh skill install cognyai/claude-code-marketing-skills subject-line-labInstalls for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).
$ npx skills add cognyai/claude-code-marketing-skills --skill subject-line-lab -a github-copilotProject install goes to .agents/skills/; add -g for ~/.copilot/skills/.
$ git clone --depth 1 https://github.com/cognyai/claude-code-marketing-skills.git skills-src && mkdir -p .github/skills && cp -r skills-src/skills/subject-line-lab .github/skills/subject-line-lab && rm -rf skills-srcUse ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.
GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/
Install the "subject-line-lab" agent skill from https://github.com/cognyai/claude-code-marketing-skills/tree/main/skills/subject-line-lab into .github/skills/subject-line-lab/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "subject-line-lab", then confirm the skill loads.GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add cognyai/claude-code-marketing-skills --skill subject-line-lab -a opencodeOpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.
$ gh skill install cognyai/claude-code-marketing-skills subject-line-lab --agent opencodeProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/cognyai/claude-code-marketing-skills.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/skills/subject-line-lab .opencode/skills/subject-line-lab && rm -rf skills-srcUse ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.
OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/
Install the "subject-line-lab" agent skill from https://github.com/cognyai/claude-code-marketing-skills/tree/main/skills/subject-line-lab into .opencode/skills/subject-line-lab/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "subject-line-lab", then confirm the skill loads.OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
Facts
- Skill name
subject-line-lab- GitHub stars
- 104
- Token cost
- ~2k tokens
- SKILL.md length
- 658 words
- Files
- 1
- Skills in repo
- 47
- Repo updated
- First seen
- Licence
- None found
At a glance
Mine your actual subject-line history from Klaviyo / Mailchimp / Rule / Get a Newsletter, find the patterns that work for YOUR list, and generate tuned candidates
- Works in 8 steps: Pull send history → Compute baseline → Extract subject-line features → …
- Tasks that involve Email marketing
- SKILL.md covers Usage, Prerequisites Check, ESP tool adapter and Steps, plus 1 more section
- Reaches cogny.com
What it does
Subject Line Lab is an agent skill from cognyai/claude-code-marketing-skills. Mine your actual subject-line history from Klaviyo / Mailchimp / Rule / Get a Newsletter, find the patterns that work for YOUR list, and generate tuned candidates
Its SKILL.md is about 2k tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.
It sits in Marketing & SEO, covering Email marketing and Newsletters. It works with Mailchimp and Model Context Protocol. The repository describes itself as: Marketing skills for Claude Code — SEO audits and implementation, ad analysis, ad optimization. Free skills need no account. $9/mo for live Search Console, Bing & LinkedIn data.
When your agent uses it
- Tasks that involve Email marketing
- Tasks that involve Newsletters
Example prompts
- “/subject-line-lab”
Requirements
- Pre-approved tools (allowed-tools): mcp__cogny__klaviyo__*, mcp__cogny__mailchimp__*, mcp__cogny__rule__*, mcp__cogny__get_a_newsletter__*, mcp__cogny__create_finding, mcp__cogny__write_context_node, mcp__cogny__read_context_node, mcp__klaviyo__*, mcp__mailchimp__*, mcp__rule__*, mcp__get_a_newsletter__*, Bash, Read, Write
Workflow steps
8 steps, taken from the step headings in SKILL.md.
- Pull send history
- Compute baseline
- Extract subject-line features
- Compute lift per feature
- Identify winning patterns
- Generate tuned candidates
- Persist patterns as context
- Create a finding
What it can do on your machine
Read from SKILL.md and the folder at commit a062fb4. It shows what the files ask for, not the result of running them.
Tool permissions
Pre-approves these tools, so the agent can use them without asking each time:
mcp__cogny__klaviyo__*mcp__cogny__mailchimp__*mcp__cogny__rule__*mcp__cogny__get_a_newsletter__*mcp__cogny__create_findingmcp__cogny__write_context_nodemcp__cogny__read_context_nodemcp__klaviyo__*mcp__mailchimp__*mcp__rule__*
…and 4 more on the same allowed-tools line.
From allowed-tools in the SKILL.md frontmatter.
Runs code
No scripts in the folder and no shell commands in SKILL.md (its code samples are json).
From the folder's file list and the shell code blocks in SKILL.md.
Network
Hosts in commands or code, which the agent is likely to contact:
cogny.com
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.
Context cost
Subject Line Lab loads about 2k tokens when it runs. Until then it costs about 45 tokens; SKILL.md has 658 words of instructions outside code blocks.
Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.
Safety
Auto-check: notes
The automated check noted patterns worth knowing about, such as sudo or a known installer.
- NotePre-approves every shell command (allowed-tools: Bash)SKILL.md
allowed-tools: mcp__cogny__klaviyo__*, mcp__cogny__mailchimp__*, mcp__cogny__rule__*, mcp__cogny__get_a_newsletter_
Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.
SKILL.md
Without a licence we can't republish the file, so here is its outline and opening line. It has 658 words (~1,998 tokens).
“Stop A/B testing blind. This skill reads your actual last 100+ sends, finds the subject-line patterns that correlate with open rate on your list, and generates 20 tuned candidates for your next campaign.”
- name
- subject-line-lab
- allowed-tools
- mcp__cogny__klaviyo__*, mcp__cogny__mailchimp__*, mcp__cogny__rule__*, mcp__cogny__get_a_newsletter__*, mcp__cogny__create_finding, mcp__cogny__write_context_node, mcp__cogny__read_context_node, mcp__klaviyo__*, mcp__mailchimp__*, mcp__rule__*, mcp__get_a_newsletter__*, Bash, Read, Write
- version
- 1.0.0
- author
- Cogny AI
- requires
- cogny-mcp
- platforms
- klaviyo, mailchimp, rule, get-a-newsletter
- user-invocable
- true
- argument-hint
- [campaign topic]
Files
Just SKILL.md in skills/subject-line-lab of cognyai/claude-code-marketing-skills.
Open the folder on GitHubat commit a062fb4
Compare with similar skills
Subject Line Lab next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.
| Skill | Stars | Used in | Tokens | Auto-check | Licence | Repo updated |
|---|---|---|---|---|---|---|
| Subject Line Lab this skillcognyai/claude-code-marketing-skills | 104 | — | ~2k | Automated safety check: Notes | None | |
| Email Marketing BibleCosmoBlk/email-marketing-bible | 330 | — | ~4.3k | Automated safety check: Pass | MIT | |
| Email Campaignsirinabuht12-oss/email-campaigns-claude | 158 | — | ~2.9k | Automated safety check: Notes | MIT | |
| Klaviyoasgeirtj/system_prompts_leaks | 69k | — | ~1.1k | Automated safety check: Pass | CC0-1.0 | |
| 49 HTML Email Template Globalminhnv0807/ai-business-skills | 609 | — | ~2.6k | Automated safety check: Pass | MIT | |
| Email Marketingshawnpang/startup-founder-skills | 343 | — | ~1.9k | Automated safety check: Pass | MIT |
Similar skills
Email Campaigns
irinabuht12-oss/email-campaigns-claude
Design, build, and send beautiful HTML email campaigns via Resend.
Klaviyo
asgeirtj/system_prompts_leaks
Read and manage the user's Klaviyo email and SMS marketing campaigns, newsletters, flows, subscriber lists, and audience segments.
49 HTML Email Template Global
minhnv0807/ai-business-skills
A skill your agent uses when responsive HTML email has to render correctly in every client — table-based structure, inline CSS, 600px max width, dark mode handling, quirks for Gmail, Apple Mail…
Email Marketing
shawnpang/startup-founder-skills
When the user needs to design, write, or optimize email sequences -- including welcome series, nurture campaigns, re-engagement flows, onboarding emails, or newsletter strategy.
Send Email Campaign
indranilbanerjee/digital-marketing-pro
Send an email campaign via a connected ESP with spam and compliance checks, approval-gated.
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Related
Works with
Categories
Questions about Subject Line Lab
What does Subject Line Lab do?
Mine your actual subject-line history from Klaviyo / Mailchimp / Rule / Get a Newsletter, find the patterns that work for YOUR list, and generate tuned candidates. Subject Line Lab is an agent skill from cognyai/claude-code-marketing-skills.
When should I use Subject Line Lab?
Subject Line Lab fits situations like: tasks that involve Email marketing; tasks that involve Newsletters.
How do I install Subject Line Lab in Claude Code?
Run `npx skills add cognyai/claude-code-marketing-skills --skill subject-line-lab -a claude-code`. Or copy the skill folder (skills/subject-line-lab in cognyai/claude-code-marketing-skills) into .claude/skills/subject-line-lab in your project. Claude Code loads it when a task matches its description.
How do I install Subject Line Lab in Codex?
Run `npx skills add cognyai/claude-code-marketing-skills --skill subject-line-lab -a codex`. Or copy the skill folder (skills/subject-line-lab in cognyai/claude-code-marketing-skills) into .agents/skills/subject-line-lab in your project. Codex loads it when a task matches its description.
Can I use Subject Line Lab in Cursor, Gemini CLI or GitHub Copilot?
Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add cognyai/claude-code-marketing-skills --skill subject-line-lab -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/subject-line-lab, .gemini/skills/subject-line-lab, .github/skills/subject-line-lab and .opencode/skills/subject-line-lab in your project.
What does Subject Line Lab need to run?
SKILL.md names no scripts, command-line tools or credentials: Subject Line Lab is instructions for the agent only. Its frontmatter pre-approves these tools: mcp__cogny__klaviyo__*, mcp__cogny__mailchimp__*, mcp__cogny__rule__*, mcp__cogny__get_a_newsletter__*, mcp__cogny__create_finding, mcp__cogny__write_context_node, mcp__cogny__read_context_node, mcp__klaviyo__*, mcp__mailchimp__*, mcp__rule__*, mcp__get_a_newsletter__*, Bash, Read, Write.
Does Subject Line Lab access the network?
SKILL.md names 1 domain. In commands or code: cogny.com; the agent is likely to contact it when it follows the instructions. This is read from the text; nothing was executed.
Is Subject Line Lab safe to install?
Our automated static check of SKILL.md found notes only (pre-approves every shell command (allowed-tools: bash)), nothing it rates as a warning. It is not a guarantee. Review the folder before installing.
What licence does Subject Line Lab use?
No licence was found for Subject Line Lab or its repository. Without one, default copyright applies: ask the author before reusing or redistributing it.
How many tokens does Subject Line Lab use?
About 2k tokens (SKILL.md is roughly 8k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.
What are the alternatives to Subject Line Lab?
Skills that share tags, products or a category with Subject Line Lab: Email Marketing Bible (CosmoBlk/email-marketing-bible, 330 stars), Email Campaigns (irinabuht12-oss/email-campaigns-claude, 158 stars), Klaviyo (asgeirtj/system_prompts_leaks, 69k stars) and 49 HTML Email Template Global (minhnv0807/ai-business-skills, 609 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.
Who maintains Subject Line Lab?
cognyai (a GitHub organization) maintains it in cognyai/claude-code-marketing-skills, which has 104 GitHub stars. The repository holds 47 skills in this directory. The repository was last updated on June 16, 2026.
Source: cognyai/claude-code-marketing-skills on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.