Agent-Skills.md

Agent Skills: Resend Email API

Resend email API via curl. Use this skill to send transactional emails, manage contacts, domains, and API keys.

apiRESTcurltransactional-emailapi-key-management
integrationID: vm0-ai/vm0-skills/resend

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vm0-ai/vm0-skills
vm0-ai
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resend/SKILL.md

Skill Metadata

Name
resend
Description
Resend email API via curl. Use this skill to send transactional emails, manage contacts, domains, and API keys.

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

  • Documentation: https://resend.com/docs/api-reference/introduction
  • Dashboard: https://resend.com/overview
  • API Keys: https://resend.com/api-keys
  • Domains: https://resend.com/domains