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.
npx skills add OpenClaudia/openclaudia-skills --skill email-subject-linesgit clone --depth 1 https://github.com/OpenClaudia/openclaudia-skillsWrote 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.
[](https://agentmods.dev/skills/openclaudia/openclaudia-skills/email-subject-lines)<a href="https://agentmods.dev/skills/openclaudia/openclaudia-skills/email-subject-lines"><img src="https://agentmods.dev/badge/skills/openclaudia/openclaudia-skills/email-subject-lines/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.
<a href="https://agentmods.dev/skills/openclaudia/openclaudia-skills/email-subject-lines"><img src="https://agentmods.dev/badge/skills/openclaudia/openclaudia-skills/email-subject-lines.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- Socket pass
- Snyk pass
- NVIDIA SkillSpector warn
SkillSpector: 3 findings, up to medium
These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →
- medium Output Handling · line 32 Output size or generation rate is not bounded. Unbounded output enables denial-of-service through resource exhaustion, log flooding, or context-window stuffing.Fix: Set explicit limits on output length, generation count, and rate. Use max_tokens and truncation to prevent unbounded output.
- medium Data Exfiltration · line 274 Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.Fix: Verify the destination URL is trusted and necessary. Remove or replace with documented APIs. Ensure no secrets, tokens, or PII are transmitted.
- medium Data Exfiltration · line 274 Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.Fix: Verify the destination URL is trusted and necessary. Remove or replace with documented APIs. Ensure no secrets, tokens, or PII are transmitted.
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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00078 | $0.03154 |
| Opus 5 | $0.00039 | $0.01577 |
| Sonnet 5 | $0.00016 | $0.00631 |
| Haiku 4.5 | $0.00008 | $0.00315 |
Grade A, and why
email-subject-lines scanned grade A with 1 finding 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 12d 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.
Makes network callslowCapability
Not a fault in itself. Listed so you know the mod talks to something, and to what.
curl -X POST https://api.resend.com/emails/batch \ How it starts
The opening of the file, as written. The whole thing — 333 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Email Subject Lines Skill
You are an email subject line specialist. Your job is to generate high-performing subject lines that maximize open rates while maintaining trust and deliverability.
Gathering Requirements
Before generating subject lines, collect these inputs:
- Email purpose - Newsletter, promotional, transactional, nurture, announcement, etc.
- Content summary - What is the email about? (2-3 sentences)
- Audience - Who is receiving this? Segment details.
- Tone - Professional, casual, urgent, playful, mysterious.
- Brand voice - Any specific do's or don'ts?
- Historical data - Past subject lines that performed well or poorly (if available).
- Quantity needed - How many options? (Default: 10 options with 3 recommended A/B pairs)
Character Length Optimization
| Length | Characters | Use For | Why |
|---|---|---|---|
| Short | 20-30 chars | Mobile-first, curiosity-driven | Fully visible on all devices, punchy |
| Medium | 30-50 chars | Most email types (sweet spot) | Enough info without truncation |
| Long | 50-70 chars | Descriptive, B2B, newsletters | More context, but truncated on mobile |
| Very long | 70+ chars | Avoid | Truncated everywhere, looks spammy |
Target: 30-50 characters (6-10 words). This range is fully visible on mobile and desktop.
Mobile preview widths:
- iPhone: ~35-40 characters
- Android: ~33-43 characters
- Gmail app: ~40 characters
Subject Line Formulas
1. Curiosity Gap
Create an information gap that can only be closed by opening the email.
Pattern: Hint at valuable information without revealing it.
| Example | Why It Works |
|---|---|
| "The one metric you're probably ignoring" | Implies they are missing something important |
| "We analyzed 10K emails. Here's what we found." | Teases data without giving the answer |
| "This changed how I think about pricing" | Personal revelation without the detail |
| "The mistake killing your conversion rate" | Specific problem, unnamed solution |
| "I was wrong about cold email" | Contrarian + personal admission |
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.
- 12d ago First seen · 333 lines · 78 tokens per session scan A 314bf56aba26
email-subject-lines is a skill published in the GitHub repository OpenClaudia/openclaudia-skills (689 stars, last pushed today), licensed MIT. It adds 78 tokens to every session and 3,154 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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