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 mailgun/mailgun-plugins --skill address-validationgit clone --depth 1 https://github.com/mailgun/mailgun-pluginsWrote 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/mailgun/mailgun-plugins/address-validation)<a href="https://agentmods.dev/skills/mailgun/mailgun-plugins/address-validation"><img src="https://agentmods.dev/badge/skills/mailgun/mailgun-plugins/address-validation/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/mailgun/mailgun-plugins/address-validation"><img src="https://agentmods.dev/badge/skills/mailgun/mailgun-plugins/address-validation.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 | $0.00026 | $0.00549 |
| Opus 5.5 | $0.00010 | $0.00220 |
| Sonnet 5.5 | $0.00005 | $0.00110 |
| Haiku 4.5 | $0.00003 | $0.00055 |
Grade A, and why
address-validation 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 2mo 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.
How it starts
The opening of the file, as written. The whole thing — 46 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Address Validation
Use this skill when the user wants to check an email address, improve signup quality, review a recipient sample, or reduce bounce and complaint risk before importing or sending to a list.
Use campaign preflight when validation is one part of a broader send-readiness review. Use bounce and suppression analysis when the address is already suppressed or has prior failure history.
MCP Scope
The packaged MCP exposes single-address validation through Mailgun Validate. Do not claim that this plugin can run Mailgun bulk validation jobs, list health previews, or download bulk result files unless those tools are added to the MCP server later.
Intake
Ask for the address or sampled addresses, region, workflow purpose, whether the address is for transactional or marketing mail, and whether the user wants a recommendation or only raw validation results.
Workflow
- Validate each address or sample address with the Mailgun Validate tool.
- Review result, risk, disposable address flag, role address flag, typo suggestion, and engagement signal when available.
- For signup or checkout, recommend blocking or warning on invalid, high risk, disposable, or typo-suspected addresses.
- For marketing, treat catch-all, role, disposable, high risk, or unknown results more cautiously than low risk deliverable addresses.
- For imported lists, validate a representative sample first and recommend a full list hygiene process when sample quality is poor.
- Check suppressions before recommending a send to an address that has previously bounced, complained, or unsubscribed.
- Return an action-oriented result: accept, warn, correct typo, suppress, review manually, or do not send.
Interpretation
- Result and risk are separate signals. A deliverable address can still be risky.
- Catch-all domains may accept mail for nonexistent recipients, so treat them as uncertain for marketing.
- Role addresses such as
info@orsupport@can be acceptable for transactional mail but risky for campaigns. - Disposable addresses are usually poor candidates for account creation and marketing lists.
- Typo suggestions should be surfaced to the user rather than silently rewriting the address.
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.
- 2mo ago First seen · 46 lines · 26 tokens per session scan A e9950b8c6874
address-validation is a skill published in the GitHub repository mailgun/mailgun-plugins (2 stars, last pushed 15d ago), licensed Apache-2.0. It adds 26 tokens to every session and 549 once invoked, about $0.0001 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 2026-08-31.
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