# How to integrate Resend MCP with Mastra AI ```json { "title": "How to integrate Resend MCP with Mastra AI", "toolkit": "Resend", "toolkit_slug": "resend", "framework": "Mastra AI", "framework_slug": "mastra-ai", "url": "https://composio.dev/toolkits/resend/framework/mastra-ai", "markdown_url": "https://composio.dev/toolkits/resend/framework/mastra-ai.md", "updated_at": "2026-05-12T10:23:58.563Z" } ``` ## Introduction This guide walks you through connecting Resend to Mastra AI using the Composio tool router. By the end, you'll have a working Resend agent that can create a new contact for your newsletter, list all domains connected to your account, cancel a scheduled marketing email through natural language commands. This guide will help you understand how to give your Mastra AI agent real control over a Resend account through Composio's Resend MCP server. Before we dive in, let's take a quick look at the key ideas and tools involved. ## Also integrate Resend with - [OpenAI Agents SDK](https://composio.dev/toolkits/resend/framework/open-ai-agents-sdk) - [Claude Agent SDK](https://composio.dev/toolkits/resend/framework/claude-agents-sdk) - [Claude Code](https://composio.dev/toolkits/resend/framework/claude-code) - [Claude Cowork](https://composio.dev/toolkits/resend/framework/claude-cowork) - [Codex](https://composio.dev/toolkits/resend/framework/codex) - [OpenClaw](https://composio.dev/toolkits/resend/framework/openclaw) - [Hermes](https://composio.dev/toolkits/resend/framework/hermes-agent) - [CLI](https://composio.dev/toolkits/resend/framework/cli) - [Google ADK](https://composio.dev/toolkits/resend/framework/google-adk) - [LangChain](https://composio.dev/toolkits/resend/framework/langchain) - [Vercel AI SDK](https://composio.dev/toolkits/resend/framework/ai-sdk) - [LlamaIndex](https://composio.dev/toolkits/resend/framework/llama-index) - [CrewAI](https://composio.dev/toolkits/resend/framework/crew-ai) ## TL;DR Here's what you'll learn: - Set up your environment so Mastra, OpenAI, and Composio work together - Create a Tool Router session in Composio that exposes Resend tools - Connect Mastra's MCP client to the Composio generated MCP URL - Fetch Resend tool definitions and attach them as a toolset - Build a Mastra agent that can reason, call tools, and return structured results - Run an interactive CLI where you can chat with your Resend agent ## What is Mastra AI? Mastra AI is a TypeScript framework for building AI agents with tool support. It provides a clean API for creating agents that can use external services through MCP. Key features include: - MCP Client: Built-in support for Model Context Protocol servers - Toolsets: Organize tools into logical groups - Step Callbacks: Monitor and debug agent execution - OpenAI Integration: Works with OpenAI models via @ai-sdk/openai ## What is the Resend MCP server, and what's possible with it? The Resend MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to your Resend account. It provides structured and secure access to your email sending and contact management capabilities, so your agent can perform actions like sending emails, managing audiences, creating domains, and handling contacts on your behalf. - Automated email delivery and scheduling: Ask your agent to send emails instantly or schedule them for later, and even cancel scheduled messages if needed. - Audience and contact management: Let your agent create, list, or delete audiences and individual contacts, keeping your recipient lists organized without manual effort. - Domain administration: Easily have your agent set up, list, or remove email sending domains, streamlining onboarding or maintenance for your email infrastructure. - Seamless recipient segmentation: Direct your agent to group contacts into audiences for targeted campaigns or communications, improving personalization and reach. - Bulk operations and cleanups: Enable your agent to quickly list, update, or delete multiple contacts, audiences, or domains to maintain a tidy and up-to-date email system. ## Supported Tools | Tool slug | Name | Description | |---|---|---| | `RESEND_ADD_CONTACT_TO_SEGMENT` | Add Contact To Segment | Add an existing contact to a segment in Resend. Use when you need to organize contacts into specific segments for targeted communication. | | `RESEND_CANCEL_EMAIL` | Cancel Email | Cancel a scheduled email. | | `RESEND_CREATE_API_KEY` | Create API Key | Create a new API key to authenticate communications with Resend. Use when you need to generate a new authentication token for API access. | | `RESEND_CREATE_AUDIENCE` | Create Audience | Create a list of contacts. | | `RESEND_CREATE_CONTACT` | Create Contact | Create a contact in Resend. | | `RESEND_CREATE_CONTACT_PROPERTY` | Create Contact Property | Tool to create a new contact property in Resend. Use when you need to define custom fields for contacts. | | `RESEND_CREATE_CONTACT_V2` | Create Contact V2 | Tool to create a new contact in Resend. Use when you need to add a contact to Resend without specifying an audience. | | `RESEND_CREATE_DOMAIN` | Create Domain | Create a domain through the Resend Email API. The domain is created in a pending/unverified state and cannot be used for sending emails until DNS verification is completed. | | `RESEND_CREATE_TEMPLATE` | Create Template | Tool to create a new email template in Resend. Use when you need to define reusable email templates with optional variables. | | `RESEND_CREATE_TOPIC` | Create Topic | Tool to create a new topic to segment your audience. Use when you need to create a topic for organizing contacts by interests or preferences. | | `RESEND_CREATE_WEBHOOK` | Create Webhook | Tool to create a webhook to receive real-time notifications about email events. Use when you need to set up automated notifications for email status changes. | | `RESEND_DELETE_API_KEY` | Delete API Key | Remove an existing API key from Resend. Use when you need to revoke or delete an API key. | | `RESEND_DELETE_AUDIENCE` | Delete Audience | Remove an existing audience. | | `RESEND_DELETE_CONTACT` | Delete Contact | Delete a contact in Resend. | | `RESEND_DELETE_CONTACT_BY_ID` | Delete Contact By ID | Tool to remove an existing contact by its ID. Use when you need to delete a contact directly without specifying an audience. | | `RESEND_DELETE_CONTACT_PROPERTY` | Delete Contact Property | Remove an existing contact property from Resend. | | `RESEND_DELETE_DOMAIN` | Delete Domain | Delete a domain through the Resend Email API. Deletion is irreversible; ensure no active email traffic or DNS configurations depend on the domain before calling. | | `RESEND_DELETE_SEGMENT` | Delete Segment | Remove an existing segment. Use when you need to permanently delete a segment by its ID. | | `RESEND_DELETE_TEMPLATE` | Delete Template | Remove an existing template. Use this action when you need to delete a template from Resend. | | `RESEND_DELETE_TOPIC` | Delete Topic | Tool to remove an existing topic in Resend. Use when you need to delete a topic. | | `RESEND_DELETE_WEBHOOK` | Delete Webhook | Remove an existing webhook. Use this to delete a webhook configuration when you no longer need to receive event notifications at that endpoint. | | `RESEND_DUPLICATE_TEMPLATE` | Duplicate Template | Duplicate an existing template through the Resend Email API. Use when you need to create a copy of an existing template. | | `RESEND_GET_CONTACT` | Get Contact | Tool to retrieve a single contact from Resend by ID or email. Use when you need to get details of a specific contact using the global contacts endpoint. | | `RESEND_GET_CONTACT_PROPERTY` | Get Contact Property | Tool to retrieve a single contact property from Resend. Use when you need to get details about a specific contact property by its ID. | | `RESEND_GET_EMAIL_ATTACHMENT` | Get Email Attachment | Retrieve a single attachment from a sent email. Use when you need to access attachment metadata and download URL. | | `RESEND_GET_SEGMENT` | Get Segment | Retrieve a single segment by its ID. Use when you need to get detailed information about a specific segment. | | `RESEND_GET_TEMPLATE` | Get Template | Retrieve a single template by ID or alias from Resend. Use when you need to view template details. | | `RESEND_GET_TOPIC` | Get Topic | Tool to retrieve a single topic by its ID in Resend. Use when you need to fetch details of a specific topic. | | `RESEND_GET_WEBHOOK` | Get Webhook | Retrieve a single webhook for the authenticated user. Use this to get details about a specific webhook configuration including its endpoint, subscribed events, and signing secret. | | `RESEND_LIST_ALL_CONTACTS` | List All Contacts | Tool to retrieve a list of all contacts from Resend. Use when you need to fetch contacts across all audiences with optional pagination. | | `RESEND_LIST_API_KEYS` | List API Keys | Tool to retrieve a list of API keys for the authenticated user. Use when you need to view all API keys associated with the account, including pagination support for large result sets. | | `RESEND_LIST_AUDIENCES` | List Audiences | List all audiences. | | `RESEND_LIST_BROADCASTS` | List Broadcasts | Tool to retrieve a list of broadcasts. Use when you need to fetch all broadcasts or paginate through them. | | `RESEND_LIST_CONTACT_PROPERTIES` | List Contact Properties | Tool to retrieve a list of contact properties from Resend. Use when you need to view available contact property definitions. | | `RESEND_LIST_CONTACTS` | List Contacts | List contacts in Resend. | | `RESEND_LIST_CONTACT_SEGMENTS` | List Contact Segments | Retrieve a list of segments that a contact is part of. Use when you need to determine which segments a specific contact belongs to. | | `RESEND_LIST_CONTACT_TOPICS` | List Contact Topics | Retrieve a list of topic subscriptions for a contact in Resend. Use when you need to check which topics a specific contact is subscribed to. | | `RESEND_LIST_DOMAINS` | List Domains | List all domains. Use the returned domain IDs as inputs for tools like RESEND_VERIFY_DOMAIN that require a domain_id. | | `RESEND_LIST_EMAIL_ATTACHMENTS` | List Email Attachments | Tool to retrieve a list of attachments from a sent email. Use when you need to get information about files attached to an email sent via Resend. | | `RESEND_LIST_EMAILS` | List Emails | Tool to retrieve a list of emails sent by your team. Use when you need to fetch outbound emails from your account. Supports pagination with limit, after, and before parameters. | | `RESEND_LIST_RECEIVED_EMAILS` | List Received Emails | Tool to retrieve a list of received emails for the authenticated user. Use when you need to fetch incoming emails from the receiving endpoint. | | `RESEND_LIST_SEGMENTS` | List Segments | Tool to retrieve a list of segments from Resend. Use when you need to view all available segments for audience management. | | `RESEND_LIST_TEMPLATES` | List Templates | Tool to retrieve a list of templates from Resend. Use when you need to get all available templates with optional pagination support. | | `RESEND_LIST_TOPICS` | List Topics | Tool to retrieve a list of topics for the authenticated user. Use when you need to fetch available topics with optional pagination support. | | `RESEND_LIST_WEBHOOKS` | List Webhooks | Retrieve a list of webhooks for the authenticated user. Use this to view all configured webhooks with their endpoints, event types, and status. | | `RESEND_PUBLISH_TEMPLATE` | Publish Template | Publish a template through the Resend Email API. Use when you need to make a template publicly available. | | `RESEND_REMOVE_CONTACT_FROM_SEGMENT` | Remove Contact From Segment | Remove an existing contact from a segment. Use when you need to disassociate a contact from a specific segment. | | `RESEND_RETRIEVE_AUDIENCE` | Retrieve Audience | Retrieve a single audience. | | `RESEND_RETRIEVE_CONTACT` | Retrieve Contact | Retrieve a contact in Resend. | | `RESEND_RETRIEVE_DOMAIN` | Retrieve Domain | Retrieve a single domain. | | `RESEND_RETRIEVE_EMAIL` | Retrieve Email | Retrieve a single email. | | `RESEND_SEND_BATCH_EMAILS` | Send Batch Emails | Trigger up to 100 batch emails at once. Use when you need to send multiple emails in a single API request. | | `RESEND_SEND_EMAIL` | Send Email | Send an email using Resend. Confirm recipients and content with the user before invoking — sends are irreversible. All recipients must be listed explicitly via `to`, `cc`, or `bcc`; audience-based sending is unsupported. Render HTML or plain text externally before passing via `html` or `text`. | | `RESEND_UPDATE_BROADCAST` | Update Broadcast | Update an existing broadcast in Resend. Use when you need to modify broadcast details like name, subject, content, or recipients. | | `RESEND_UPDATE_CONTACT` | Update Contact | Tool to update an existing contact in Resend by ID or email. Use when you need to modify contact details such as name or subscription status. | | `RESEND_UPDATE_CONTACT_PROPERTY` | Update Contact Property | Update an existing contact property in Resend. Only the fallback_value can be updated; the key and type fields cannot be changed after creation. | | `RESEND_UPDATE_DOMAIN` | Update Domain | Update an existing domain. | | `RESEND_UPDATE_EMAIL` | Update Email | Update a scheduled email. | | `RESEND_UPDATE_TEMPLATE` | Update Template | Tool to update an existing email template in Resend. Use when you need to modify template properties such as name, subject, HTML content, or variables. | | `RESEND_UPDATE_TOPIC` | Update Topic | Tool to update an existing topic in Resend. Use when you need to modify the name of a topic. | | `RESEND_UPDATE_WEBHOOK` | Update Webhook | Tool to update an existing webhook configuration. Use when you need to modify the endpoint URL, change event subscriptions, or enable/disable a webhook. | | `RESEND_VERIFY_DOMAIN` | Verify Domain | Verify a domain through the Resend Email API. DNS records must fully propagate before verification succeeds; avoid immediate retries after DNS setup. | ## Supported Triggers None listed. ## Creating MCP Server - Stand-alone vs Composio SDK The Resend MCP server is an implementation of the Model Context Protocol that connects your AI agent to Resend. It provides structured and secure access so your agent can perform Resend operations on your behalf through a secure, permission-based interface. With Composio's managed implementation, you don't have to create your own developer app. For production, if you're building an end product, we recommend using your own credentials. The managed server helps you prototype fast and go from 0-1 faster. ## Step-by-step Guide ### 1. Prerequisites Before starting, make sure you have: - Node.js 18 or higher - A Composio account with an active API key - An OpenAI API key - Basic familiarity with TypeScript ### 1. Getting API Keys for OpenAI and Composio OpenAI API Key - Go to the [OpenAI dashboard](https://platform.openai.com/settings/organization/api-keys) and create an API key. - You need credits or a connected billing setup to use the models. - Store the key somewhere safe. Composio API Key - Log in to the [Composio dashboard](https://dashboard.composio.dev?utm_source=toolkits&utm_medium=framework_docs). - Go to Settings and copy your API key. - This key lets your Mastra agent talk to Composio and reach Resend through MCP. ### 2. Install dependencies Install the required packages. What's happening: - @composio/core is the Composio SDK for creating MCP sessions - @mastra/core provides the Agent class - @mastra/mcp is Mastra's MCP client - @ai-sdk/openai is the model wrapper for OpenAI - dotenv loads environment variables from .env ```bash npm install @composio/core @mastra/core @mastra/mcp @ai-sdk/openai dotenv ``` ### 3. Set up environment variables Create a .env file in your project root. What's happening: - COMPOSIO_API_KEY authenticates your requests to Composio - COMPOSIO_USER_ID tells Composio which user this session belongs to - OPENAI_API_KEY lets the Mastra agent call OpenAI models ```bash COMPOSIO_API_KEY=your_composio_api_key_here COMPOSIO_USER_ID=your_user_id_here OPENAI_API_KEY=your_openai_api_key_here ``` ### 4. Import libraries and validate environment What's happening: - dotenv/config auto loads your .env so process.env.* is available - openai gives you a Mastra compatible model wrapper - Agent is the Mastra agent that will call tools and produce answers - MCPClient connects Mastra to your Composio MCP server - Composio is used to create a Tool Router session ```typescript import "dotenv/config"; import { openai } from "@ai-sdk/openai"; import { Agent } from "@mastra/core/agent"; import { MCPClient } from "@mastra/mcp"; import { Composio } from "@composio/core"; import * as readline from "readline"; import type { AiMessageType } from "@mastra/core/agent"; const openaiAPIKey = process.env.OPENAI_API_KEY; const composioAPIKey = process.env.COMPOSIO_API_KEY; const composioUserID = process.env.COMPOSIO_USER_ID; if (!openaiAPIKey) throw new Error("OPENAI_API_KEY is not set"); if (!composioAPIKey) throw new Error("COMPOSIO_API_KEY is not set"); if (!composioUserID) throw new Error("COMPOSIO_USER_ID is not set"); const composio = new Composio({ apiKey: composioAPIKey as string, }); ``` ### 5. Create a Tool Router session for Resend What's happening: - create spins up a short-lived MCP HTTP endpoint for this user - The toolkits array contains "resend" for Resend access - session.mcp.url is the MCP URL that Mastra's MCPClient will connect to ```typescript async function main() { const session = await composio.create( composioUserID as string, { toolkits: ["resend"], }, ); const composioMCPUrl = session.mcp.url; console.log("Resend MCP URL:", composioMCPUrl); ``` ### 6. Configure Mastra MCP client and fetch tools What's happening: - MCPClient takes an id for this client and a list of MCP servers - The headers property includes the x-api-key for authentication - getTools fetches the tool definitions exposed by the Resend toolkit ```typescript const mcpClient = new MCPClient({ id: composioUserID as string, servers: { nasdaq: { url: new URL(composioMCPUrl), requestInit: { headers: session.mcp.headers, }, }, }, timeout: 30_000, }); console.log("Fetching MCP tools from Composio..."); const composioTools = await mcpClient.getTools(); console.log("Number of tools:", Object.keys(composioTools).length); ``` ### 7. Create the Mastra agent What's happening: - Agent is the core Mastra agent - name is just an identifier for logging and debugging - instructions guide the agent to use tools instead of only answering in natural language - model uses openai("gpt-5") to configure the underlying LLM ```typescript const agent = new Agent({ name: "resend-mastra-agent", instructions: "You are an AI agent with Resend tools via Composio.", model: "openai/gpt-5", }); ``` ### 8. Set up interactive chat interface What's happening: - messages keeps the full conversation history in Mastra's expected format - agent.generate runs the agent with conversation history and Resend toolsets - maxSteps limits how many tool calls the agent can take in a single run - onStepFinish is a hook that prints intermediate steps for debugging ```typescript let messages: AiMessageType[] = []; console.log("Chat started! Type 'exit' or 'quit' to end.\n"); const rl = readline.createInterface({ input: process.stdin, output: process.stdout, prompt: "> ", }); rl.prompt(); rl.on("line", async (userInput: string) => { const trimmedInput = userInput.trim(); if (["exit", "quit", "bye"].includes(trimmedInput.toLowerCase())) { console.log("\nGoodbye!"); rl.close(); process.exit(0); } if (!trimmedInput) { rl.prompt(); return; } messages.push({ id: crypto.randomUUID(), role: "user", content: trimmedInput, }); console.log("\nAgent is thinking...\n"); try { const response = await agent.generate(messages, { toolsets: { resend: composioTools, }, maxSteps: 8, }); const { text } = response; if (text && text.trim().length > 0) { console.log(`Agent: ${text}\n`); messages.push({ id: crypto.randomUUID(), role: "assistant", content: text, }); } } catch (error) { console.error("\nError:", error); } rl.prompt(); }); rl.on("close", async () => { console.log("\nSession ended."); await mcpClient.disconnect(); process.exit(0); }); } main().catch((err) => { console.error("Fatal error:", err); process.exit(1); }); ``` ## Complete Code ```typescript import "dotenv/config"; import { openai } from "@ai-sdk/openai"; import { Agent } from "@mastra/core/agent"; import { MCPClient } from "@mastra/mcp"; import { Composio } from "@composio/core"; import * as readline from "readline"; import type { AiMessageType } from "@mastra/core/agent"; const openaiAPIKey = process.env.OPENAI_API_KEY; const composioAPIKey = process.env.COMPOSIO_API_KEY; const composioUserID = process.env.COMPOSIO_USER_ID; if (!openaiAPIKey) throw new Error("OPENAI_API_KEY is not set"); if (!composioAPIKey) throw new Error("COMPOSIO_API_KEY is not set"); if (!composioUserID) throw new Error("COMPOSIO_USER_ID is not set"); const composio = new Composio({ apiKey: composioAPIKey as string }); async function main() { const session = await composio.create(composioUserID as string, { toolkits: ["resend"], }); const composioMCPUrl = session.mcp.url; const mcpClient = new MCPClient({ id: composioUserID as string, servers: { resend: { url: new URL(composioMCPUrl), requestInit: { headers: session.mcp.headers, }, }, }, timeout: 30_000, }); const composioTools = await mcpClient.getTools(); const agent = new Agent({ name: "resend-mastra-agent", instructions: "You are an AI agent with Resend tools via Composio.", model: "openai/gpt-5", }); let messages: AiMessageType[] = []; const rl = readline.createInterface({ input: process.stdin, output: process.stdout, prompt: "> ", }); rl.prompt(); rl.on("line", async (input: string) => { const trimmed = input.trim(); if (["exit", "quit"].includes(trimmed.toLowerCase())) { rl.close(); return; } messages.push({ id: crypto.randomUUID(), role: "user", content: trimmed }); const { text } = await agent.generate(messages, { toolsets: { resend: composioTools }, maxSteps: 8, }); if (text) { console.log(`Agent: ${text}\n`); messages.push({ id: crypto.randomUUID(), role: "assistant", content: text }); } rl.prompt(); }); rl.on("close", async () => { await mcpClient.disconnect(); process.exit(0); }); } main(); ``` ## Conclusion You've built a Mastra AI agent that can interact with Resend through Composio's Tool Router. You can extend this further by: - Adding other toolkits like Gmail, Slack, or GitHub - Building a web-based chat interface around this agent - Using multiple MCP endpoints to enable cross-app workflows ## How to build Resend MCP Agent with another framework - [OpenAI Agents SDK](https://composio.dev/toolkits/resend/framework/open-ai-agents-sdk) - [Claude Agent SDK](https://composio.dev/toolkits/resend/framework/claude-agents-sdk) - [Claude Code](https://composio.dev/toolkits/resend/framework/claude-code) - [Claude Cowork](https://composio.dev/toolkits/resend/framework/claude-cowork) - [Codex](https://composio.dev/toolkits/resend/framework/codex) - [OpenClaw](https://composio.dev/toolkits/resend/framework/openclaw) - [Hermes](https://composio.dev/toolkits/resend/framework/hermes-agent) - [CLI](https://composio.dev/toolkits/resend/framework/cli) - [Google ADK](https://composio.dev/toolkits/resend/framework/google-adk) - [LangChain](https://composio.dev/toolkits/resend/framework/langchain) - [Vercel AI SDK](https://composio.dev/toolkits/resend/framework/ai-sdk) - [LlamaIndex](https://composio.dev/toolkits/resend/framework/llama-index) - [CrewAI](https://composio.dev/toolkits/resend/framework/crew-ai) ## Related Toolkits - [Reddit](https://composio.dev/toolkits/reddit) - Reddit is a social news platform with thriving user-driven communities (subreddits). It's the go-to place for discussion, content sharing, and viral marketing. - [Facebook](https://composio.dev/toolkits/facebook) - Facebook is a social media and advertising platform for businesses and creators. It helps you connect, share, and manage content across your public Facebook Pages. - [Linkedin](https://composio.dev/toolkits/linkedin) - LinkedIn is a professional networking platform for connecting, sharing content, and engaging with business opportunities. It's the go-to place for building your professional brand and unlocking new career connections. - [Active campaign](https://composio.dev/toolkits/active_campaign) - ActiveCampaign is a marketing automation and CRM platform for managing email campaigns, sales pipelines, and customer segmentation. It helps businesses engage customers and drive growth through smart automation and targeted outreach. - [ActiveTrail](https://composio.dev/toolkits/active_trail) - ActiveTrail is a user-friendly email marketing and automation platform. It helps you reach subscribers and automate campaigns with ease. - [Ahrefs](https://composio.dev/toolkits/ahrefs) - Ahrefs is an SEO and marketing platform for site audits, keyword research, and competitor insights. It helps you improve search rankings and drive organic traffic. - [Amcards](https://composio.dev/toolkits/amcards) - AMCards lets you create and mail personalized greeting cards online. Build stronger customer relationships with easy, automated card campaigns. - [Beamer](https://composio.dev/toolkits/beamer) - Beamer is a news and changelog platform for in-app announcements and feature updates. It helps companies boost user engagement by sharing news where users are most active. - [Benchmark email](https://composio.dev/toolkits/benchmark_email) - Benchmark Email is a platform for creating, sending, and tracking email campaigns. It's built to help you engage audiences and analyze results—all in one place. - [Bigmailer](https://composio.dev/toolkits/bigmailer) - BigMailer is an email marketing platform for managing multiple brands with white-labeling and automation. It helps teams streamline campaigns and simplify integration with Amazon SES. - [Brandfetch](https://composio.dev/toolkits/brandfetch) - Brandfetch is an API that delivers company logos, colors, and visual branding assets. It helps marketers and developers keep brand visuals consistent everywhere. - [Brevo](https://composio.dev/toolkits/brevo) - Brevo is an all-in-one email and SMS marketing platform for transactional messaging, automation, and CRM. It helps businesses engage customers and streamline communications through powerful campaign tools. - [Campayn](https://composio.dev/toolkits/campayn) - Campayn is an email marketing platform for creating, sending, and managing campaigns. It helps businesses engage contacts and grow audiences with easy-to-use tools. - [Cardly](https://composio.dev/toolkits/cardly) - Cardly is a platform for creating and sending personalized direct mail to customers. It helps businesses break through the digital clutter by getting real engagement via physical mailboxes. - [ClickSend](https://composio.dev/toolkits/clicksend) - ClickSend is a cloud-based SMS and email marketing platform for businesses. It streamlines communication by enabling quick message delivery and contact management. - [Crustdata](https://composio.dev/toolkits/crustdata) - CrustData is an AI-powered data intelligence platform for real-time company and people data. It helps B2B sales teams, AI SDRs, and investors react to live business signals. - [Curated](https://composio.dev/toolkits/curated) - Curated is a platform for collecting, curating, and publishing newsletters. It streamlines content aggregation and distribution for creators and teams. - [Customerio](https://composio.dev/toolkits/customerio) - Customer.io is a customer engagement platform for targeted messaging across email, SMS, and push. Easily automate, segment, and track communications with your audience. - [Cutt ly](https://composio.dev/toolkits/cutt_ly) - Cutt.ly is a URL shortening service for managing and analyzing links. Streamline your workflows with quick, trackable, and branded short URLs. - [Demio](https://composio.dev/toolkits/demio) - Demio is webinar software built for marketers, offering both live and automated sessions with interactive features. It helps teams engage audiences and optimize lead generation through detailed analytics. ## Frequently Asked Questions ### What are the differences in Tool Router MCP and Resend MCP? With a standalone Resend MCP server, the agents and LLMs can only access a fixed set of Resend tools tied to that server. However, with the Composio Tool Router, agents can dynamically load tools from Resend and many other apps based on the task at hand, all through a single MCP endpoint. ### Can I use Tool Router MCP with Mastra AI? Yes, you can. Mastra AI fully supports MCP integration. You get structured tool calling, message history handling, and model orchestration while Tool Router takes care of discovering and serving the right Resend tools. ### Can I manage the permissions and scopes for Resend while using Tool Router? Yes, absolutely. You can configure which Resend scopes and actions are allowed when connecting your account to Composio. You can also bring your own OAuth credentials or API configuration so you keep full control over what the agent can do. ### How safe is my data with Composio Tool Router? All sensitive data such as tokens, keys, and configuration is fully encrypted at rest and in transit. Composio is SOC 2 Type 2 compliant and follows strict security practices so your Resend data and credentials are handled as safely as possible. --- [See all toolkits](https://composio.dev/toolkits) · [Composio docs](https://docs.composio.dev/llms.txt)