Resend

What it does

When your agent uses it

• Working with the Resend email API — sending transactional emails (single
• Receiving inbound emails via webhooks
• Managing email templates
• Tracking delivery events

Example prompts

• “send an email with Resend”
• “/resend”

Requirements

• Python 3
• Node.js
• A credential in RESEND_API_KEY
• A credential in RESEND_WEBHOOK_SECRET

Workflow steps

3 steps, taken from the first numbered list in SKILL.md.

1. 1Set up inbound domain first (see receiving.md)
2. 2Set up sending (see sending/overview.md)
3. 3Note: batch sending does NOT support attachments or scheduling — use single sends when forwarding with attachments

What it can do on your machine

Read from SKILL.md and the folder at commit c30c8ff. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  Ships script files (JavaScript, from the files we listed), which the agent can run.

  Shell commands in SKILL.md call:

  • npm
  • pip
  • go
  • gem
  • composer
  • cargo
  • dotnet

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  Links to these hosts (documentation or services it may open):

  • resend.com

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names these keys or tokens, usually read from environment variables:

  • RESEND_API_KEY
  • RESEND_WEBHOOK_SECRET

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Resend loads about 3.6k tokens when it runs, and up to ~42k if it reads all its reference files. Until then it costs about 145 tokens; SKILL.md has 1,078 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~145

When it runs · the whole SKILL.md, loaded when a task matches

~3.6k

With references · SKILL.md plus every file in references/, read only if the agent opens them

~42k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from Asymmetric-al/core at commit c30c8ff, republished under its MIT licence (© Asymmetric-al). 1,078 words, ~3,573 tokens.

name

resend

description

Use when working with the Resend email API — sending transactional emails (single or batch), receiving inbound emails via webhooks, managing email templates, tracking delivery events, managing domains, contacts, broadcasts, webhooks, API keys, automations, events, viewing API request logs, or setting up the Resend SDK. Always use this skill when the user mentions Resend, even for simple tasks like "send an email with Resend" — the skill contains critical gotchas (idempotency keys, webhook verification, template variable syntax) that prevent common production issues.

license

MIT

metadata.author

resend

metadata.version

3.10.0

metadata.homepage

https://resend.com/agent-skills

metadata.source

https://github.com/resend/resend-skills

references

sending, receiving.md, templates.md, webhooks.md, domains.md, contacts.md, broadcasts.md, api-keys.md, logs.md, contact-properties.md, segments.md, topics.md…

import { Resend } from 'resend';

const resend = new Resend(process.env.RESEND_API_KEY);

const { data, error } = await resend.emails.send(
  {
    from: 'Acme <onboarding@resend.dev>',
    to: ['delivered@resend.dev'],
    subject: 'Hello World',
    html: '<p>Email body here</p>',
  },
  { idempotencyKey: `welcome-email/${userId}` }
);

if (error) {
  console.error('Failed:', error.message);
  return;
}
console.log('Sent:', data.id);

import resend
import os

resend.api_key = os.environ["RESEND_API_KEY"]

email = resend.Emails.send({
    "from": "Acme <onboarding@resend.dev>",
    "to": ["delivered@resend.dev"],
    "subject": "Hello World",
    "html": "<p>Email body here</p>",
}, idempotency_key=f"welcome-email/{user_id}")

import { Resend } from 'resend';

const resend = new Resend(process.env.RESEND_API_KEY);

export async function POST(req: Request) {
  const payload = await req.text(); // Must use raw text, not req.json()

  const event = resend.webhooks.verify({
    payload,
    headers: {
      'svix-id': req.headers.get('svix-id'),
      'svix-timestamp': req.headers.get('svix-timestamp'),
      'svix-signature': req.headers.get('svix-signature'),
    },
    secret: process.env.RESEND_WEBHOOK_SECRET,
  });

  if (event.type === 'email.received') {
    // Webhook has metadata only — call API for body
    const { data: email } = await resend.emails.receiving.get(
      event.data.email_id
    );
    console.log(email.text);
  }

  return new Response('OK', { status: 200 });
}

export RESEND_API_KEY=re_xxxxxxxxx

© Asymmetric-al, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 20 other files (references) in .agents/skills/resend of Asymmetric-al/core.

• SKILL.md
• references/api-keys.md
• references/automations.md
• references/broadcasts.md
• references/contact-properties.md
• references/contacts.md
• references/domains.md
• references/events.md
• references/fetch-all-templates.mjs
• references/installation.md
• references/logs.md
• references/receiving.md
• references/segments.md
• references/sending/batch-email-examples.md
• references/sending/best-practices.md
• references/sending/email-management.md
• references/sending/overview.md
• references/sending/single-email-examples.md
• references/templates.md
• … and 2 more

Open the folder on GitHubat commit c30c8ff