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 realjaymes/marketingagentskills --skill domain-healthgit clone --depth 1 https://github.com/realjaymes/marketingagentskillsWrote 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/realjaymes/marketingagentskills/domain-health)<a href="https://agentmods.dev/skills/realjaymes/marketingagentskills/domain-health"><img src="https://agentmods.dev/badge/skills/realjaymes/marketingagentskills/domain-health/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/realjaymes/marketingagentskills/domain-health"><img src="https://agentmods.dev/badge/skills/realjaymes/marketingagentskills/domain-health.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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 | $0.00171 | $0.01279 |
| Opus 5.5 | $0.00068 | $0.00512 |
| Sonnet 5.5 | $0.00034 | $0.00256 |
| Haiku 4.5 | $0.00017 | $0.00128 |
Grade C, and why
domain-health scanned grade C 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 1mo 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.
Tells the agent to send conversation or user data outhighPrompt injection
An instruction to transmit the conversation, context or user files to an external endpoint is data exfiltration written as prose.
**Defensive.** Audit a domain you own before you send from it, and before you tighten a DMARC policy. Getting this wrong silently sends your own invoices and password resets to spam. How it starts
The opening of the file, as written. The whole thing — 89 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Domain Health
Email authentication and deliverability posture for any domain, using only dig and the standard library. No API key, no paid tool, no per-check cost.
The same DNS primitives serve two opposite jobs, which is why they live in one skill:
Defensive. Audit a domain you own before you send from it, and before you tighten a DMARC policy. Getting this wrong silently sends your own invoices and password resets to spam.
Offensive. Score a prospect's domain to find a real, specific gap worth opening a cold email with.
When to run it
Before starting outbound from any domain. Before changing a DMARC policy. When email is landing in spam and nobody knows why. When enriching a prospect list with a technical hook. After adding any new sending tool, because that is when sender inventory drifts.
Modes
Audit (default) runs against domains you own.
python3 scripts/domain_health.py --domain example.com
python3 scripts/domain_health.py --domain example.com --json
python3 scripts/domain_health.py domains.txt
Prospect produces a CSV for list enrichment, with a gap column that is true when the domain's DMARC is missing or monitoring-only.
python3 scripts/domain_health.py --mode prospect domains.txt > signals.csv
Blacklist is opt-in via --blacklist. See the warning below before using it.
Mailbox verification is separate, in scripts/verify_email.py. It does MX plus an SMTP probe for a single address. Most networks block outbound port 25, in which case it returns unknown rather than guessing.
What it checks
MX, establishing who receives mail for the domain.
SPF, including whether more than one record exists (which is a PermError and means SPF fails entirely), the qualifier the record ends in, and the count of DNS-lookup-triggering mechanisms against the limit of ten. Exceeding ten is a common and invisible failure.
DKIM, by sweeping a maintained list of per-provider selectors in scripts/selectors.json.
What ships with it
6 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 1mo ago First seen · 89 lines · 171 tokens per session scan C 158d46c26e2d
domain-health is a skill published in the GitHub repository realjaymes/marketingagentskills (68 stars, last pushed 2d ago), licensed MIT. It adds 171 tokens to every session and 1,279 once invoked, about $0.0007 per session on Opus 5.5. A static security scan graded it C with 1 finding (tells the agent to send conversation or user data out). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-23.
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