Overview

The Resend MCP Server integrates the Resend transactional email API into the Model Context Protocol (MCP) ecosystem, providing a lightweight, programmable email tool that can be called from agents, workflows, or other MCP-aware services. It wraps common email operations—sending messages, using templates, attaching files, and checking delivery status—behind a consistent MCP tool interface so you can integrate reliable transactional email into automation and agent-driven flows.

This server is useful when you need programmatic, auditable email delivery as part of a larger AI or automation system. It centralizes configuration (API keys, templates, retries), exposes monitoring endpoints, and supports delivery events so you can track and react to bounces or opens without wiring directly to the Resend API from every service.

Features

Send transactional emails (HTML/text) via Resend
Use Resend templates with per-recipient template data
Support for attachments and custom headers
Delivery and bounce handling via webhooks/events
Retry/backoff for transient failures
Structured logging and basic metrics (health, uptime)
Configurable rate limits and concurrency controls
Docker-friendly and environment-driven configuration

Installation / Configuration

Requirements: Node.js 18+ (or the runtime specified in the repository), npm or yarn, and a Resend API key.

Clone the repository and install dependencies:

git clone https://github.com/Klavis-AI/klavis.git
cd klavis/mcp_servers/resend
npm install
# or
yarn install

Configure environment variables (example .env):

# .env
RESEND_API_KEY=rev_live_XXXXXXXXXXXXXXXXXXXX
MCP_PORT=8080
LOG_LEVEL=info
MAX_CONCURRENCY=10
RETRY_ATTEMPTS=3
RETRY_BACKOFF_MS=500
WEBHOOK_SECRET=my-webhook-secret

Key configuration variables

Variable	Description	Default / Notes
RESEND_API_KEY	Your Resend API key (required)	—
MCP_PORT	HTTP port the MCP server listens on	8080
LOG_LEVEL	Logging level (debug, info, warn, error)	info
MAX_CONCURRENCY	Maximum parallel outbound sends	10
RETRY_ATTEMPTS	Number of retry attempts on transient failures	3
RETRY_BACKOFF_MS	Base backoff in milliseconds for retries	500
WEBHOOK_SECRET	Signing secret for webhook verification	optional but recommended

Run locally:

npm run start
# or
node dist/index.js

Docker (example):

# docker-compose.yml
version: '3.8'
services:
  resend-mcp:
    image: klavis/resend-mcp:latest
    ports:
      - "8080:8080"
    environment:
      - RESEND_API_KEY=${RESEND_API_KEY}
      - MCP_PORT=8080
      - LOG_LEVEL=info

Available Tools / Resources

The Resend MCP Server exposes a small set of MCP tools and HTTP endpoints. Tools are described here in a generic form—refer to the repository for exact field names.

send_email — Send a single transactional email.
- Fields: to, from, subject, text, html, template_id, template_data, cc, bcc, attachments, headers, metadata, tags
send_batch — Send multiple personalized messages in a single operation (batching + concurrency control)
get_status — Query delivery status or fetch message metadata by message_id
health — Liveness and readiness endpoints for orchestration
webhook_receiver — Endpoint to accept Resend events (delivered, bounced, opened, clicked)

Example: send_email (MCP tool payload)

{
  "tool": "send_email",
  "args": {
    "to": ["[email protected]"],
    "from": "[email protected]",
    "subject": "Reset your password",
    "html": "<p>Hi {{name}}, click <a href='{{reset_link}}'>here</a> to reset.</p>",
    "template_id": null,
    "template_data": { "name": "Alice", "reset_link": "https://..." },
    "metadata": { "account_id": "acct_123" }
  }
}

Example response:

{
  "message_id": "msg_abc123",
  "status": "queued",
  "provider": "resend",
  "sent_at": "2026-04-10T12:34:56Z"
}

Webhook verification: the server can validate incoming Resend webhook requests using WEBHOOK_SECRET, and will emit structured events to your MCP runtime or a configured event sink.

Use Cases

Password reset flows: Trigger a single templated email from your authentication agent when a user requests a password reset. Include secure, expiring links in template_data.
Receipts and invoices: Automatically attach a PDF invoice to an order confirmation email using attachments and metadata for reconciliation.
Multi-step agent workflows: An AI agent generates a personalized onboarding sequence, calls send_email for each step, and uses delivery events to advance or retry steps if delivery fails.
Error & alerting notifications: Dispatch timed alerts from automated monitoring workflows with structured metadata to correlate with incidents.
Bulk personalization: Send a batch of personalized transactional messages (e.g., billing reminders) while respecting concurrency/rate limits and tracking per-recipient success/failure.

Monitoring & Best Practices

Enable webhooks to capture bounces and deliveries; treat bounces as signals to update user contact status.
Configure reasonable concurrency and retry_backoff values to avoid rate limiting from Resend.
Log message_id and provider responses for audit and troubleshooting.
Use templates for consistent formatting and smaller payloads; pass per-recipient data rather than building full HTML in the caller.

For complete API details, advanced configuration options, and repository-specific instructions, see the code and README in the GitHub repository: https://github.com/Klavis-AI/klavis/tree/main/mcp_servers/resend

Resend MCP Server for Transactional Email