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@vm0-ai/vm0-skills
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Resend email API via curl. Use this skill to send transactional emails, manage contacts, domains, and API keys.

Install Skill

1Download skill
2Enable skills in Claude

Open claude.ai/settings/capabilities and find the "Skills" section

3Upload to Claude

Click "Upload skill" and select the downloaded ZIP file

Note: Please verify skill by going through its instructions before using it.

SKILL.md

name resend
description Resend email API via curl. Use this skill to send transactional emails, manage contacts, domains, and API keys.
vm0_secrets RESEND_API_KEY

Resend Email API

Send transactional emails, manage contacts, and domains via Resend's REST API.

Official docs: https://resend.com/docs/api-reference/introduction

When to Use

Use this skill when you need to:

  • Send transactional emails (welcome, password reset, notifications)
  • Send batch emails to multiple recipients
  • Manage email contacts and audiences
  • Verify and manage sending domains
  • Track email delivery status

Prerequisites

  1. Sign up at https://resend.com
  2. Go to API Keys: https://resend.com/api-keys
  3. Create a new API key

Set environment variable:

export RESEND_API_KEY="re_xxxxxxxxx"

Important: When using $VAR in a command that pipes to another command, wrap the command containing $VAR in bash -c '...'. Due to a Claude Code bug, environment variables are silently cleared when pipes are used directly.

Placeholders: Values in {curly-braces} like {email-id} are placeholders. Replace them with actual values when executing.

Emails

Send Email

Write to /tmp/resend_request.json:

{
  "from": "Acme <onboarding@resend.dev>",
  "to": ["<your-recipient-email>"],
  "subject": "<your-subject>",
  "html": "<p><your-html-content></p>"
}

Then run:

bash -c 'curl -s -X POST "https://api.resend.com/emails" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d @/tmp/resend_request.json'

Send Email with Plain Text

Write to /tmp/resend_request.json:

{
  "from": "Acme <onboarding@resend.dev>",
  "to": ["<your-recipient-email>"],
  "subject": "<your-subject>",
  "text": "<your-plain-text-content>"
}

Then run:

bash -c 'curl -s -X POST "https://api.resend.com/emails" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d @/tmp/resend_request.json'

Send Email with CC/BCC

Write to /tmp/resend_request.json:

{
  "from": "Acme <onboarding@resend.dev>",
  "to": ["<your-recipient-email>"],
  "cc": ["<your-cc-email>"],
  "bcc": ["<your-bcc-email>"],
  "subject": "<your-subject>",
  "html": "<p><your-html-content></p>"
}

Then run:

bash -c 'curl -s -X POST "https://api.resend.com/emails" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d @/tmp/resend_request.json'

Send Email with Reply-To

Write to /tmp/resend_request.json:

{
  "from": "Acme <onboarding@resend.dev>",
  "to": ["<your-recipient-email>"],
  "replyTo": "<your-reply-to-email>",
  "subject": "<your-subject>",
  "html": "<p><your-html-content></p>"
}

Then run:

bash -c 'curl -s -X POST "https://api.resend.com/emails" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d @/tmp/resend_request.json'

Send Scheduled Email

Schedule email using natural language or ISO 8601 format:

Write to /tmp/resend_request.json:

{
  "from": "Acme <onboarding@resend.dev>",
  "to": ["<your-recipient-email>"],
  "subject": "<your-subject>",
  "html": "<p><your-html-content></p>",
  "scheduledAt": "in 1 hour"
}

Then run:

bash -c 'curl -s -X POST "https://api.resend.com/emails" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d @/tmp/resend_request.json'

Send Batch Emails

Send up to 100 emails in a single request:

Write to /tmp/resend_request.json:

[
  {
    "from": "Acme <onboarding@resend.dev>",
    "to": ["<your-recipient-1>"],
    "subject": "Hello 1",
    "html": "<p>Email 1</p>"
  },
  {
    "from": "Acme <onboarding@resend.dev>",
    "to": ["<your-recipient-2>"],
    "subject": "Hello 2",
    "html": "<p>Email 2</p>"
  }
]

Then run:

bash -c 'curl -s -X POST "https://api.resend.com/emails/batch" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d @/tmp/resend_request.json'

Retrieve Email

bash -c 'curl -s "https://api.resend.com/emails/<your-email-id>" --header "Authorization: Bearer $RESEND_API_KEY"'

List Sent Emails

bash -c 'curl -s "https://api.resend.com/emails" --header "Authorization: Bearer $RESEND_API_KEY"'

Cancel Scheduled Email

bash -c 'curl -s -X POST "https://api.resend.com/emails/<your-email-id>/cancel" --header "Authorization: Bearer $RESEND_API_KEY"'

Contacts

Create Contact

Write to /tmp/resend_request.json:

{
  "email": "<your-contact-email>",
  "firstName": "<your-first-name>",
  "lastName": "<your-last-name>",
  "unsubscribed": false
}

Then run:

bash -c 'curl -s -X POST "https://api.resend.com/contacts" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d @/tmp/resend_request.json'

Create Contact with Custom Properties

Write to /tmp/resend_request.json:

{
  "email": "<your-contact-email>",
  "firstName": "<your-first-name>",
  "lastName": "<your-last-name>",
  "properties": {
    "company": "<your-company-name>",
    "role": "<your-role>"
  }
}

Then run:

bash -c 'curl -s -X POST "https://api.resend.com/contacts" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d @/tmp/resend_request.json'

Retrieve Contact

bash -c 'curl -s "https://api.resend.com/contacts/<your-contact-id>" --header "Authorization: Bearer $RESEND_API_KEY"'

List Contacts

bash -c 'curl -s "https://api.resend.com/contacts" --header "Authorization: Bearer $RESEND_API_KEY"'

List Contacts with Pagination

bash -c 'curl -s "https://api.resend.com/contacts?limit=50" --header "Authorization: Bearer $RESEND_API_KEY"'

Update Contact

Write to /tmp/resend_request.json:

{
  "firstName": "<your-new-first-name>",
  "unsubscribed": true
}

Then run:

bash -c 'curl -s -X PATCH "https://api.resend.com/contacts/<your-contact-id>" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d @/tmp/resend_request.json'

Delete Contact

bash -c 'curl -s -X DELETE "https://api.resend.com/contacts/<your-contact-id>" --header "Authorization: Bearer $RESEND_API_KEY"'

Domains

List Domains

bash -c 'curl -s "https://api.resend.com/domains" --header "Authorization: Bearer $RESEND_API_KEY"'

Retrieve Domain

bash -c 'curl -s "https://api.resend.com/domains/<your-domain-id>" --header "Authorization: Bearer $RESEND_API_KEY"'

Create Domain

Write to /tmp/resend_request.json:

{
  "name": "<your-domain-name>"
}

Then run:

bash -c 'curl -s -X POST "https://api.resend.com/domains" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d @/tmp/resend_request.json'

Verify Domain

bash -c 'curl -s -X POST "https://api.resend.com/domains/<your-domain-id>/verify" --header "Authorization: Bearer $RESEND_API_KEY"'

Delete Domain

bash -c 'curl -s -X DELETE "https://api.resend.com/domains/<your-domain-id>" --header "Authorization: Bearer $RESEND_API_KEY"'

API Keys

List API Keys

bash -c 'curl -s "https://api.resend.com/api-keys" --header "Authorization: Bearer $RESEND_API_KEY"'

Create API Key

Write to /tmp/resend_request.json:

{
  "name": "<your-key-name>"
}

Then run:

bash -c 'curl -s -X POST "https://api.resend.com/api-keys" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d @/tmp/resend_request.json'

Create API Key with Permissions

Write to /tmp/resend_request.json:

{
  "name": "<your-key-name>",
  "permission": "sending_access"
}

Then run:

bash -c 'curl -s -X POST "https://api.resend.com/api-keys" --header "Authorization: Bearer $RESEND_API_KEY" --header "Content-Type: application/json" -d @/tmp/resend_request.json'

Delete API Key

bash -c 'curl -s -X DELETE "https://api.resend.com/api-keys/<your-api-key-id>" --header "Authorization: Bearer $RESEND_API_KEY"'

Email Parameters Reference

Parameter Type Description
from string Sender email (required). Format: "Name <email@domain.com>"
to string[] Recipients (required). Max 50 addresses
subject string Email subject (required)
html string HTML content
text string Plain text content
cc string[] CC recipients
bcc string[] BCC recipients
replyTo string Reply-to address
scheduledAt string Schedule time (ISO 8601 or natural language)
tags array Custom tags for tracking
attachments array File attachments (max 40MB total)

Response Codes

Status Description
200 Success
400 Invalid parameters
401 Missing API key
403 Invalid API key
404 Resource not found
429 Rate limit exceeded (2 req/sec)
5xx Server error

Guidelines

  1. Rate Limits: Default is 2 requests per second; implement backoff for 429 errors
  2. Sender Domain: Use verified domains for production; onboarding@resend.dev for testing
  3. Batch Emails: Use /emails/batch for sending to multiple recipients efficiently
  4. Idempotency: Use Idempotency-Key header to prevent duplicate sends
  5. Scheduling: Use natural language (in 1 hour) or ISO 8601 format for scheduledAt

API Reference