Agent Skills: resend

Troubleshooting

If requests fail, run zero doctor check-connector --env-name RESEND_TOKEN or zero doctor check-connector --url https://api.resend.com/emails --method POST

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:

curl -s -X POST "https://api.resend.com/emails" --header "Authorization: Bearer $RESEND_TOKEN" --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:

curl -s -X POST "https://api.resend.com/emails" --header "Authorization: Bearer $RESEND_TOKEN" --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:

curl -s -X POST "https://api.resend.com/emails" --header "Authorization: Bearer $RESEND_TOKEN" --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>"],
  "reply_to": "<your-reply-to-email>",
  "subject": "<your-subject>",
  "html": "<p><your-html-content></p>"
}

Then run:

curl -s -X POST "https://api.resend.com/emails" --header "Authorization: Bearer $RESEND_TOKEN" --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>",
  "scheduled_at": "in 1 hour"
}

Then run:

curl -s -X POST "https://api.resend.com/emails" --header "Authorization: Bearer $RESEND_TOKEN" --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:

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

Retrieve Email

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

List Sent Emails

curl -s "https://api.resend.com/emails" --header "Authorization: Bearer $RESEND_TOKEN"

Cancel Scheduled Email

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

Contacts

Create Contact

Write to /tmp/resend_request.json:

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

Then run:

curl -s -X POST "https://api.resend.com/contacts" --header "Authorization: Bearer $RESEND_TOKEN" --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>",
  "first_name": "<your-first-name>",
  "last_name": "<your-last-name>",
  "properties": {
    "company": "<your-company-name>",
    "role": "<your-role>"
  }
}

Then run:

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

Retrieve Contact

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

List Contacts

curl -s "https://api.resend.com/contacts" --header "Authorization: Bearer $RESEND_TOKEN"

List Contacts with Pagination

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

Update Contact

Write to /tmp/resend_request.json:

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

Then run:

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

Delete Contact

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

Domains

List Domains

curl -s "https://api.resend.com/domains" --header "Authorization: Bearer $RESEND_TOKEN"

Retrieve Domain

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

Create Domain

Write to /tmp/resend_request.json:

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

Then run:

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

Verify Domain

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

Delete Domain

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

API Keys

List API Keys

curl -s "https://api.resend.com/api-keys" --header "Authorization: Bearer $RESEND_TOKEN"

Create API Key

Write to /tmp/resend_request.json:

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

Then run:

curl -s -X POST "https://api.resend.com/api-keys" --header "Authorization: Bearer $RESEND_TOKEN" --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:

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

Delete API Key

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

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 | | reply_to | string | Reply-to address | | scheduled_at | 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 scheduled_at

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