agentmail-sending

agentmail-sending is a skill for Claude Code from desplega-ai/agent-swarm. It costs 55 tokens per session (1,336 once invoked), scanned A, original, MIT.

A reference for sending email through AgentMail, an email-sending service. It specifies the correct server address, message fields, text-only format, and example requests.

In plain words
What is it for?
Use it to send plain-text messages, add recipients or blind-copy recipients, set subjects, and choose between a direct request and a reusable script.
Why use it?
It prevents common sending failures caused by the wrong address, field names, or HTML handling, and keeps one-off emails from becoming unnecessary reusable scripts.

Skill for Claude Code

Written for Claude Code: user-invocable in frontmatter.

Good fit Use it to send plain-text messages, add recipients or blind-copy recipients, set subjects, and choose between a direct request and a reusable script.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/desplega-ai/agent-swarm/agentmail-sending
Install

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.

Any agent
npx skills add desplega-ai/agent-swarm --skill agentmail-sending
Clone the repo
git clone --depth 1 https://github.com/desplega-ai/agent-swarm

Made for: Claude Code.

Wrote 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.

agentmods badge for agentmail-sending

README.md
[![agentmods](https://agentmods.dev/badge/skills/desplega-ai/agent-swarm/agentmail-sending/github.svg)](https://agentmods.dev/skills/desplega-ai/agent-swarm/agentmail-sending)
Your own site
<a href="https://agentmods.dev/skills/desplega-ai/agent-swarm/agentmail-sending"><img src="https://agentmods.dev/badge/skills/desplega-ai/agent-swarm/agentmail-sending/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.

agentmods 80×15 button for agentmail-sending

Your own site · 80×15
<a href="https://agentmods.dev/skills/desplega-ai/agent-swarm/agentmail-sending"><img src="https://agentmods.dev/badge/skills/desplega-ai/agent-swarm/agentmail-sending.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 55 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,336 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 6 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 Data Exfiltration · line 3
    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 14
    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 47
    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 53
    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 101
    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 154
    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.
How audits are shown
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00055 $0.01336
Opus 5 $0.00028 $0.00668
Sonnet 5 $0.00011 $0.00267
Haiku 4.5 $0.00006 $0.00134

Measured 11d ago against content hash c5b00ff8670d, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

agentmail-sending 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 11d 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.

description: Canonical AgentMail send-message API reference for swarm agents. Pins the base URL, required field names, text-only rendering workaround, BCC policy, and ready-to-copy curl / swarm-script examples so agents
templates/skills/agentmail-sending/SKILL.md · 170 lines

How it starts

The opening of the file, as written. The whole thing — 170 lines — stays where its author put it; the contents beside it link to each section on GitHub.

AgentMail Sending

Canonical Base URL

Use this base URL exactly:

https://api.agentmail.to/v0/

DO NOT use api.agentmail.ai. That host is a hallucination and will not send mail through AgentMail's current API.

Canonical Send-Message Fields

For POST /inboxes/{inbox}/messages/send, the JSON body fields are exactly:

to
bcc
subject
text

Use text, NOT text_body, body, or content.

Do NOT pass html. AgentMail has a known rendering bug: when html is passed with text, the HTML body can be empty and email clients may show a blank email. AgentMail renders text correctly on its own.

Rule 0: One-Shots Stay One-Shots

For a one-off send, such as a kickoff email or a single notification, do not create a reusable swarm-script. Use raw curl from Bash, or inline script_run if you need swarm-visible execution.

Only use script_upsert when the send will be reused by a workflow that fires repeatedly.

Default Example: Raw curl

Use this direct API call first. It does not assume any SDK is installed.

Endpoint:

https://api.agentmail.to/v0/inboxes/{inbox}/messages/send
INBOX="<agentmail-inbox-id>"

curl -sS -X POST "https://api.agentmail.to/v0/inboxes/${INBOX}/messages/send" \
  -H "Authorization: Bearer $AGENTMAIL_API_KEY" \
  -H "Content-Type: application/json" \
  --data-binary @- <<'JSON'
{
  "to": ["[email protected]"],
  "bcc": ["[email protected]"],
  "subject": "Subject line",
  "text": "Plain-text email body."
}
JSON

Notes:

  • AGENTMAIL_API_KEY must be configured in swarm config or exported into the shell before running curl.
  • Keep bcc for external recipients so a human oversight inbox sees outbound email.
  • Do not add html; text is the canonical content field.

Reusable Workflow Example: script_upsert

Use this only when the send is part of a reusable workflow. The script resolves the API key from swarm config at runtime and calls the same raw HTTP endpoint with fetch.

Read the full file on GitHub · 170 lines

Files

What ships with it

2 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.

Changes

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.

  1. 11d ago First seen · 170 lines · 55 tokens per session scan A c5b00ff8670d

Subscribe to this mod's changes

agentmail-sending is a skill published in the GitHub repository desplega-ai/agent-swarm (761 stars, last pushed today), licensed MIT. It adds 55 tokens to every session and 1,336 once invoked, about $0.0003 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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