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 agentmods add skills/jtsternberg/claude-plugins/using-agentmailnpx skills add jtsternberg/claude-plugins --skill using-agentmailgit clone --depth 1 https://github.com/jtsternberg/claude-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/jtsternberg/claude-plugins/using-agentmail)<a href="https://agentmods.dev/skills/jtsternberg/claude-plugins/using-agentmail"><img src="https://agentmods.dev/badge/skills/jtsternberg/claude-plugins/using-agentmail.svg" alt="Measured on agentmods" 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 | $0.00092 | $0.06566 |
| Opus 5 | $0.00046 | $0.03283 |
| Sonnet 5 | $0.00018 | $0.01313 |
| Haiku 4.5 | $0.00009 | $0.00657 |
Grade A, and why
using-agentmail 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 3d 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.
> Then decide with the user. If a guaranteed-once send genuinely matters, drop to `curl` How it starts
The opening of the file, as written. The whole thing — 464 lines — stays where its author put it; the contents beside it link to each section on GitHub.
AgentMail
Give an agent its own email address and run a full round trip on it: create inboxes,
send, read what comes back, reply / reply-all / forward, and stage drafts for review.
Driven entirely by the official agentmail CLI.
This is AgentMail specifically — an email API built for agents, where every inbox is
an API resource. It is not the user's own mail: reading or sending the user's Gmail is the
gws plugin. It is not raw SMTP.
This is the hub. Four sibling skills go deeper
Use them instead of this file when the task is one of theirs; come back here for setup, flags, errors, and anything the others do not cover.
| Skill | For |
|---|---|
contacts |
the address book — who is who, and which address is actually verified |
check-mail |
what arrived, reading full bodies, and triaging an inbox |
replying |
reply / reply-all / forward, draft-first for anything consequential |
relay-work-order |
handing work to (or taking work from) another agent over email |
Two shared references sit at the plugin root because more than one skill needs each:
references/replying.md (the mechanics of answering mail) and
references/agent-mail-protocol.md (the [HANDOFF]/[ASK]/[FYI]/[DONE] contract).
Codex: substitute the installed plugin directory for the path below.
${CLAUDE_PLUGIN_ROOT}/references/replying.md
${CLAUDE_PLUGIN_ROOT}/references/agent-mail-protocol.md
"What is your email address?" — check, don't assume
When you're asked whether you have an email, what your address is, or whether people can write to you, the honest answer is not "I'm an agent, I don't have one" and it is never the user's own address from session context. An inbox may have been provisioned for you already. Find out before you answer:
agentmail inboxes list
If it returns an inbox, that address (and its display name) is your answer. If it returns
nothing — or the CLI/key isn't set up (run the preflight) — then say you have no inbox yet
and offer to create one. Answering an identity question from memory is how an agent with a
live @agentmail.to inbox came to tell its user, twice, that it had no email.
What ships with it
5 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.
- 3d ago First seen · 464 lines · 92 tokens per session scan A be0de73c60de
using-agentmail is a skill published in the GitHub repository jtsternberg/claude-plugins (5 stars, last pushed today), licensed MIT. It adds 92 tokens to every session and 6,566 once invoked, about $0.0005 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 2026-08-31.
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