# How to integrate Mailersend MCP with LlamaIndex

```json
{
  "title": "How to integrate Mailersend MCP with LlamaIndex",
  "toolkit": "Mailersend",
  "toolkit_slug": "mailersend",
  "framework": "LlamaIndex",
  "framework_slug": "llama-index",
  "url": "https://composio.dev/toolkits/mailersend/framework/llama-index",
  "markdown_url": "https://composio.dev/toolkits/mailersend/framework/llama-index.md",
  "updated_at": "2026-05-12T10:18:19.514Z"
}
```

## Introduction

This guide walks you through connecting Mailersend to LlamaIndex using the Composio tool router. By the end, you'll have a working Mailersend agent that can add a new sending domain for your app, list all smtp users for our domain, check current api quota usage through natural language commands.
This guide will help you understand how to give your LlamaIndex agent real control over a Mailersend account through Composio's Mailersend MCP server.
Before we dive in, let's take a quick look at the key ideas and tools involved.

## Also integrate Mailersend with

- [OpenAI Agents SDK](https://composio.dev/toolkits/mailersend/framework/open-ai-agents-sdk)
- [Claude Agent SDK](https://composio.dev/toolkits/mailersend/framework/claude-agents-sdk)
- [Claude Code](https://composio.dev/toolkits/mailersend/framework/claude-code)
- [Claude Cowork](https://composio.dev/toolkits/mailersend/framework/claude-cowork)
- [Codex](https://composio.dev/toolkits/mailersend/framework/codex)
- [OpenClaw](https://composio.dev/toolkits/mailersend/framework/openclaw)
- [Hermes](https://composio.dev/toolkits/mailersend/framework/hermes-agent)
- [CLI](https://composio.dev/toolkits/mailersend/framework/cli)
- [Google ADK](https://composio.dev/toolkits/mailersend/framework/google-adk)
- [LangChain](https://composio.dev/toolkits/mailersend/framework/langchain)
- [Vercel AI SDK](https://composio.dev/toolkits/mailersend/framework/ai-sdk)
- [Mastra AI](https://composio.dev/toolkits/mailersend/framework/mastra-ai)
- [CrewAI](https://composio.dev/toolkits/mailersend/framework/crew-ai)

## TL;DR

Here's what you'll learn:
- Set your OpenAI and Composio API keys
- Install LlamaIndex and Composio packages
- Create a Composio Tool Router session for Mailersend
- Connect LlamaIndex to the Mailersend MCP server
- Build a Mailersend-powered agent using LlamaIndex
- Interact with Mailersend through natural language

## What is LlamaIndex?

LlamaIndex is a data framework for building LLM applications. It provides tools for connecting LLMs to external data sources and services through agents and tools.
Key features include:
- ReAct Agent: Reasoning and acting pattern for tool-using agents
- MCP Tools: Native support for Model Context Protocol
- Context Management: Maintain conversation context across interactions
- Async Support: Built for async/await patterns

## What is the Mailersend MCP server, and what's possible with it?

The Mailersend MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to your Mailersend account. It provides structured and secure access to your transactional email infrastructure, so your agent can perform actions like sending emails, managing domains, configuring webhooks, and monitoring API usage on your behalf.
- Seamless domain management: Register new sending domains, verify their status, and retrieve detailed configuration information to ensure reliable email delivery.
- Automated email and SMTP user setup: Quickly create SMTP users and API tokens as needed for secure and scalable application integration.
- Webhook configuration and event tracking: Set up and delete webhooks to monitor real-time email events such as sent, delivered, or opened messages, enabling proactive workflows and notifications.
- Recipient and quota insights: List recipients for specific domains and monitor your API usage to stay within account limits and optimize deliverability.
- Centralized resource discovery: Retrieve general API resources and overview endpoints to streamline Mailersend integration and administration directly from your agent.

## Supported Tools

| Tool slug | Name | Description |
|---|---|---|
| `MAILERSEND_CREATE_DOMAIN` | Create Sending Domain | Tool to add a new sending domain to MailerSend. Use when you need to register and configure a domain before sending emails. |
| `MAILERSEND_CREATE_SMTP_USER` | Create SMTP User | Tool to create a new SMTP user. Use after domain setup to obtain SMTP credentials. |
| `MAILERSEND_CREATE_TOKEN` | Create API Token | Creates a new API token with specified scopes (permissions) for a domain. The token allows programmatic access to MailerSend API endpoints based on granted scopes. WARNING: The token value is only displayed once upon creation and cannot be retrieved later. |
| `MAILERSEND_CREATE_WEBHOOK` | Create Webhook | Tool to create a new webhook for a MailerSend domain. Use after you have a domain ID and need to receive event notifications like sent, delivered, opened, etc. |
| `MAILERSEND_DELETE_WEBHOOK` | Delete Webhook | Tool to delete an existing webhook. Use when the webhook is no longer needed. Returns empty response on successful deletion (HTTP 204). |
| `MAILERSEND_GET_API_QUOTA` | Get API Quota | Tool to retrieve current API usage quota. Use when monitoring API rate limits to avoid exceeding allowed calls. |
| `MAILERSEND_GET_DOMAIN` | Get Domain | Tool to retrieve detailed information about a specific sending domain in MailerSend. Returns domain verification status (DKIM, SPF, MX, tracking), settings (click/open tracking, paused status), and metadata (creation/update timestamps). Use this when you need to check if a domain is properly verified and configured for sending emails, or to review domain-specific tracking settings. Note: For detailed DNS record values, use the Get Domain DNS Records action. |
| `MAILERSEND_GET_DOMAIN_RECIPIENTS` | List Domain Recipients | Tool to list recipients for a domain. Use after obtaining the domain ID to view recipients with optional pagination. |
| `MAILERSEND_GET_DOMAINS` | Get sending domains | Retrieve a paginated list of all sending domains configured in your MailerSend account. Use this to: - View all domains available for sending emails - Check domain verification and DNS status - Filter by verification status to find verified or unverified domains - Review domain settings like tracking and sending preferences Returns domain details including verification status, DNS configuration, and tracking settings. |
| `MAILERSEND_GET_GENERAL_RESOURCES` | Get general API resources | Tool to retrieve general API resources and information. Use when you need an overview of all MailerSend endpoints before constructing specific calls. |
| `MAILERSEND_GET_IDENTITIES` | List Sender Identities | Retrieves a paginated list of sender identities configured in your MailerSend account. Sender identities are the email addresses or domains authorized to send emails through MailerSend. Each identity includes verification status, reply-to configuration, domain association, and optional personal notes. Use this tool to discover available sender identities before sending emails or to verify which identities are ready for use. Returns: Paginated list of identity objects with metadata including verification status, domain details, and navigation links for pagination. |
| `MAILERSEND_GET_MESSAGES` | Get sent messages | Tool to retrieve a paginated list of sent messages. Use after sending emails to view message logs. |
| `MAILERSEND_GET_RECIPIENTS` | Get email recipients | Tool to retrieve a list of email recipients. Use when you need to list and filter recipients by list ID or search term. |
| `MAILERSEND_GET_SMS_ACTIVITY` | Get SMS Activity | Tool to retrieve SMS activity logs. Use when you need to fetch delivery status and logs of sent SMS messages. |
| `MAILERSEND_GET_SMS_INBOUNDS` | Get SMS Inbounds | Retrieve inbound SMS route configurations. Inbound routes define rules for forwarding incoming SMS messages to webhook URLs based on message content filters. Use this action when you need to: - List all configured SMS inbound routes - Filter routes by SMS number or enabled status - Review webhook forwarding configurations and filter rules |
| `MAILERSEND_GET_SMS_MESSAGES` | List SMS Messages | Retrieves a paginated list of SMS messages sent through the MailerSend API. Returns message details including sender, recipients, content, status, and timestamps. Use this to review sent SMS messages and track their delivery status. Note: For detailed activity tracking with filters (date ranges, status, phone numbers), use the SMS Activity endpoint instead. |
| `MAILERSEND_GET_SMS_NUMBERS` | Get SMS Numbers | Tool to retrieve a paginated list of SMS phone numbers. Use after purchasing numbers to fetch available SMS numbers. |
| `MAILERSEND_GET_SMS_RECIPIENTS` | Get SMS recipients | Tool to retrieve a list of SMS recipients. Use when you need to list and paginate SMS recipients, optionally filtering by SMS number ID and/or recipient status. |
| `MAILERSEND_GET_SMTP_USERS` | Get SMTP users | Tool to retrieve a list of SMTP users. Use when you need to list and paginate SMTP users. |
| `MAILERSEND_GET_TEMPLATES` | Get email templates | Retrieves a paginated list of email templates from your MailerSend account. Use this tool when you need to: - List all available email templates - Filter templates by domain ID - Browse templates with pagination - Check template details like name, type, and creation date Returns template metadata including IDs, names, types, and timestamps. For full template content, use a separate get single template endpoint. |
| `MAILERSEND_GET_TOKENS` | Get API Tokens | Retrieves a paginated list of API tokens associated with your MailerSend account. Returns token details including ID, name, status, creation date, and assigned scopes/permissions. Requires 'tokens_full' scope. |
| `MAILERSEND_GET_USERS` | Get users | Tool to retrieve a list of users associated with your account. Use after authenticating with a valid API token. |
| `MAILERSEND_GET_WEBHOOKS` | List webhooks | Tool to retrieve a list of webhooks. Use when you need to list and paginate all configured webhooks, optionally filtering by domain. |

## Supported Triggers

None listed.

## Creating MCP Server - Stand-alone vs Composio SDK

The Mailersend MCP server is an implementation of the Model Context Protocol that connects your AI agent to Mailersend. It provides structured and secure access so your agent can perform Mailersend 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 you begin, make sure you have:
- Python 3.8/Node 16 or higher installed
- A Composio account with the API key
- An OpenAI API key
- A Mailersend account and project
- Basic familiarity with async Python/Typescript

### 1. Getting API Keys for OpenAI, Composio, and Mailersend

No description provided.

### 2. Installing dependencies

No description provided.
```python
pip install composio-llamaindex llama-index llama-index-llms-openai llama-index-tools-mcp python-dotenv
```

```typescript
npm install @composio/llamaindex @llamaindex/openai @llamaindex/tools @llamaindex/workflow dotenv
```

### 3. Set environment variables

Create a .env file in your project root:
These credentials will be used to:
- Authenticate with OpenAI's GPT-5 model
- Connect to Composio's Tool Router
- Identify your Composio user session for Mailersend access
```bash
OPENAI_API_KEY=your-openai-api-key
COMPOSIO_API_KEY=your-composio-api-key
COMPOSIO_USER_ID=your-user-id
```

### 4. Import modules

No description provided.
```python
import asyncio
import os
import dotenv

from composio import Composio
from composio_llamaindex import LlamaIndexProvider
from llama_index.core.agent.workflow import ReActAgent
from llama_index.core.workflow import Context
from llama_index.llms.openai import OpenAI
from llama_index.tools.mcp import BasicMCPClient, McpToolSpec

dotenv.load_dotenv()
```

```typescript
import "dotenv/config";
import readline from "node:readline/promises";
import { stdin as input, stdout as output } from "node:process";

import { Composio } from "@composio/core";

import { mcp } from "@llamaindex/tools";
import { agent as createAgent } from "@llamaindex/workflow";
import { openai } from "@llamaindex/openai";

dotenv.config();
```

### 5. Load environment variables and initialize Composio

No description provided.
```python
OPENAI_API_KEY = os.getenv("OPENAI_API_KEY")
COMPOSIO_API_KEY = os.getenv("COMPOSIO_API_KEY")
COMPOSIO_USER_ID = os.getenv("COMPOSIO_USER_ID")

if not OPENAI_API_KEY:
    raise ValueError("OPENAI_API_KEY is not set in the environment")
if not COMPOSIO_API_KEY:
    raise ValueError("COMPOSIO_API_KEY is not set in the environment")
if not COMPOSIO_USER_ID:
    raise ValueError("COMPOSIO_USER_ID is not set in the environment")
```

```typescript
const OPENAI_API_KEY = process.env.OPENAI_API_KEY;
const COMPOSIO_API_KEY = process.env.COMPOSIO_API_KEY;
const COMPOSIO_USER_ID = process.env.COMPOSIO_USER_ID;

if (!OPENAI_API_KEY) throw new Error("OPENAI_API_KEY is not set");
if (!COMPOSIO_API_KEY) throw new Error("COMPOSIO_API_KEY is not set");
if (!COMPOSIO_USER_ID) throw new Error("COMPOSIO_USER_ID is not set");
```

### 6. Create a Tool Router session and build the agent function

What's happening here:
- We create a Composio client using your API key and configure it with the LlamaIndex provider
- We then create a tool router MCP session for your user, specifying the toolkits we want to use (in this case, mailersend)
- The session returns an MCP HTTP endpoint URL that acts as a gateway to all your configured tools
- LlamaIndex will connect to this endpoint to dynamically discover and use the available Mailersend tools.
- The MCP tools are mapped to LlamaIndex-compatible tools and plug them into the Agent.
```python
async def build_agent() -> ReActAgent:
    composio_client = Composio(
        api_key=COMPOSIO_API_KEY,
        provider=LlamaIndexProvider(),
    )

    session = composio_client.create(
        user_id=COMPOSIO_USER_ID,
        toolkits=["mailersend"],
    )

    mcp_url = session.mcp.url
    print(f"Composio MCP URL: {mcp_url}")

    mcp_client = BasicMCPClient(mcp_url, headers={"x-api-key": COMPOSIO_API_KEY})
    mcp_tool_spec = McpToolSpec(client=mcp_client)
    tools = await mcp_tool_spec.to_tool_list_async()

    llm = OpenAI(model="gpt-5")

    description = "An agent that uses Composio Tool Router MCP tools to perform Mailersend actions."
    system_prompt = """
    You are a helpful assistant connected to Composio Tool Router.
    Use the available tools to answer user queries and perform Mailersend actions.
    """
    return ReActAgent(tools=tools, llm=llm, description=description, system_prompt=system_prompt, verbose=True)
```

```typescript
async function buildAgent() {

  console.log(`Initializing Composio client...${COMPOSIO_USER_ID!}...`);
  console.log(`COMPOSIO_USER_ID: ${COMPOSIO_USER_ID!}...`);

  const composio = new Composio({
    apiKey: COMPOSIO_API_KEY,
    provider: new LlamaindexProvider(),
  });

  const session = await composio.create(
    COMPOSIO_USER_ID!,
    {
      toolkits: ["mailersend"],
    },
  );

  const mcpUrl = session.mcp.url;
  console.log(`Composio Tool Router MCP URL: ${mcpUrl}`);

  const server = mcp({
    url: mcpUrl,
    clientName: "composio_tool_router_with_llamaindex",
    requestInit: {
      headers: {
        "x-api-key": COMPOSIO_API_KEY!,
      },
    },
    // verbose: true,
  });

  const tools = await server.tools();

  const llm = openai({ apiKey: OPENAI_API_KEY, model: "gpt-5" });

  const agent = createAgent({
    name: "composio_tool_router_with_llamaindex",
        description : "An agent that uses Composio Tool Router MCP tools to perform actions.",
    systemPrompt:
      "You are a helpful assistant connected to Composio Tool Router."+
"Use the available tools to answer user queries and perform Mailersend actions." ,
    llm,
    tools,
  });

  return agent;
}
```

### 7. Create an interactive chat loop

No description provided.
```python
async def chat_loop(agent: ReActAgent) -> None:
    ctx = Context(agent)
    print("Type 'quit', 'exit', or Ctrl+C to stop.")

    while True:
        try:
            user_input = input("\nYou: ").strip()
        except (KeyboardInterrupt, EOFError):
            print("\nBye!")
            break

        if not user_input or user_input.lower() in {"quit", "exit"}:
            print("Bye!")
            break

        try:
            print("Agent: ", end="", flush=True)
            handler = agent.run(user_input, ctx=ctx)

            async for event in handler.stream_events():
                # Stream token-by-token from LLM responses
                if hasattr(event, "delta") and event.delta:
                    print(event.delta, end="", flush=True)
                # Show tool calls as they happen
                elif hasattr(event, "tool_name"):
                    print(f"\n[Using tool: {event.tool_name}]", flush=True)

            # Get final response
            response = await handler
            print()  # Newline after streaming
        except KeyboardInterrupt:
            print("\n[Interrupted]")
            continue
        except Exception as e:
            print(f"\nError: {e}")
```

```typescript
async function chatLoop(agent: ReturnType<typeof createAgent>) {
  const rl = readline.createInterface({ input, output });

  console.log("Type 'quit' or 'exit' to stop.");

  while (true) {
    let userInput: string;

    try {
      userInput = (await rl.question("\nYou: ")).trim();
    } catch {
      console.log("\nAgent: Bye!");
      break;
    }

    if (!userInput) {
      continue;
    }

    const lower = userInput.toLowerCase();
    if (lower === "quit" || lower === "exit") {
      console.log("Agent: Bye!");
      break;
    }

    try {
      process.stdout.write("Agent: ");

      const stream = agent.runStream(userInput);
      let finalResult: any = null;

      for await (const event of stream) {
        // The event.data contains the streamed content
        const data: any = event.data;

        // Check for streaming delta content
        if (data?.delta) {
          process.stdout.write(data.delta);
        }

        // Store final result for fallback
        if (data?.result || data?.message) {
          finalResult = data;
        }
      }

      // If no streaming happened, show the final result
      if (finalResult) {
        const answer =
          finalResult.result ??
          finalResult.message?.content ??
          finalResult.message ??
          "";
        if (answer && typeof answer === "string" && !answer.includes("[object")) {
          process.stdout.write(answer);
        }
      }

      console.log(); // New line after streaming completes
    } catch (err: any) {
      console.error("\nAgent error:", err?.message ?? err);
    }
  }

  rl.close();
}
```

### 8. Define the main entry point

What's happening here:
- We're orchestrating the entire application flow
- The agent gets built with proper error handling
- Then we kick off the interactive chat loop so you can start talking to Mailersend
```python
async def main() -> None:
    agent = await build_agent()
    await chat_loop(agent)

if __name__ == "__main__":
    # Handle Ctrl+C gracefully
    signal.signal(signal.SIGINT, lambda s, f: (print("\nBye!"), exit(0)))
    try:
        asyncio.run(main())
    except KeyboardInterrupt:
        print("\nBye!")
```

```typescript
async function main() {
  try {
    const agent = await buildAgent();
    await chatLoop(agent);
  } catch (err) {
    console.error("Failed to start agent:", err);
    process.exit(1);
  }
}

main();
```

### 9. Run the agent

When prompted, authenticate and authorise your agent with Mailersend, then start asking questions.
```bash
python llamaindex_agent.py
```

```typescript
npx ts-node llamaindex-agent.ts
```

## Complete Code

```python
import asyncio
import os
import signal
import dotenv

from composio import Composio
from composio_llamaindex import LlamaIndexProvider
from llama_index.core.agent.workflow import ReActAgent
from llama_index.core.workflow import Context
from llama_index.llms.openai import OpenAI
from llama_index.tools.mcp import BasicMCPClient, McpToolSpec

dotenv.load_dotenv()

OPENAI_API_KEY = os.getenv("OPENAI_API_KEY")
COMPOSIO_API_KEY = os.getenv("COMPOSIO_API_KEY")
COMPOSIO_USER_ID = os.getenv("COMPOSIO_USER_ID")

if not OPENAI_API_KEY:
    raise ValueError("OPENAI_API_KEY is not set")
if not COMPOSIO_API_KEY:
    raise ValueError("COMPOSIO_API_KEY is not set")
if not COMPOSIO_USER_ID:
    raise ValueError("COMPOSIO_USER_ID is not set")

async def build_agent() -> ReActAgent:
    composio_client = Composio(
        api_key=COMPOSIO_API_KEY,
        provider=LlamaIndexProvider(),
    )

    session = composio_client.create(
        user_id=COMPOSIO_USER_ID,
        toolkits=["mailersend"],
    )

    mcp_url = session.mcp.url
    print(f"Composio MCP URL: {mcp_url}")

    mcp_client = BasicMCPClient(mcp_url, headers={"x-api-key": COMPOSIO_API_KEY})
    mcp_tool_spec = McpToolSpec(client=mcp_client)
    tools = await mcp_tool_spec.to_tool_list_async()

    llm = OpenAI(model="gpt-5")
    description = "An agent that uses Composio Tool Router MCP tools to perform Mailersend actions."
    system_prompt = """
    You are a helpful assistant connected to Composio Tool Router.
    Use the available tools to answer user queries and perform Mailersend actions.
    """
    return ReActAgent(
        tools=tools,
        llm=llm,
        description=description,
        system_prompt=system_prompt,
        verbose=True,
    );

async def chat_loop(agent: ReActAgent) -> None:
    ctx = Context(agent)
    print("Type 'quit', 'exit', or Ctrl+C to stop.")

    while True:
        try:
            user_input = input("\nYou: ").strip()
        except (KeyboardInterrupt, EOFError):
            print("\nBye!")
            break

        if not user_input or user_input.lower() in {"quit", "exit"}:
            print("Bye!")
            break

        try:
            print("Agent: ", end="", flush=True)
            handler = agent.run(user_input, ctx=ctx)

            async for event in handler.stream_events():
                # Stream token-by-token from LLM responses
                if hasattr(event, "delta") and event.delta:
                    print(event.delta, end="", flush=True)
                # Show tool calls as they happen
                elif hasattr(event, "tool_name"):
                    print(f"\n[Using tool: {event.tool_name}]", flush=True)

            # Get final response
            response = await handler
            print()  # Newline after streaming
        except KeyboardInterrupt:
            print("\n[Interrupted]")
            continue
        except Exception as e:
            print(f"\nError: {e}")

async def main() -> None:
    agent = await build_agent()
    await chat_loop(agent)

if __name__ == "__main__":
    # Handle Ctrl+C gracefully
    signal.signal(signal.SIGINT, lambda s, f: (print("\nBye!"), exit(0)))
    try:
        asyncio.run(main())
    except KeyboardInterrupt:
        print("\nBye!")
```

```typescript
import "dotenv/config";
import readline from "node:readline/promises";
import { stdin as input, stdout as output } from "node:process";

import { Composio } from "@composio/core";
import { LlamaindexProvider } from "@composio/llamaindex";

import { mcp } from "@llamaindex/tools";
import { agent as createAgent } from "@llamaindex/workflow";
import { openai } from "@llamaindex/openai";

dotenv.config();

const OPENAI_API_KEY = process.env.OPENAI_API_KEY;
const COMPOSIO_API_KEY = process.env.COMPOSIO_API_KEY;
const COMPOSIO_USER_ID = process.env.COMPOSIO_USER_ID;

if (!OPENAI_API_KEY) {
    throw new Error("OPENAI_API_KEY is not set in the environment");
  }
if (!COMPOSIO_API_KEY) {
    throw new Error("COMPOSIO_API_KEY is not set in the environment");
  }
if (!COMPOSIO_USER_ID) {
    throw new Error("COMPOSIO_USER_ID is not set in the environment");
  }

async function buildAgent() {

  console.log(`Initializing Composio client...${COMPOSIO_USER_ID!}...`);
  console.log(`COMPOSIO_USER_ID: ${COMPOSIO_USER_ID!}...`);

  const composio = new Composio({
    apiKey: COMPOSIO_API_KEY,
    provider: new LlamaindexProvider(),
  });

  const session = await composio.create(
    COMPOSIO_USER_ID!,
    {
      toolkits: ["mailersend"],
    },
  );

  const mcpUrl = session.mcp.url;
  console.log(`Composio Tool Router MCP URL: ${mcpUrl}`);

  const server = mcp({
    url: mcpUrl,
    clientName: "composio_tool_router_with_llamaindex",
    requestInit: {
      headers: {
        "x-api-key": COMPOSIO_API_KEY!,
      },
    },
    // verbose: true,
  });

  const tools = await server.tools();

  const llm = openai({ apiKey: OPENAI_API_KEY, model: "gpt-5" });

  const agent = createAgent({
    name: "composio_tool_router_with_llamaindex",
    description:
      "An agent that uses Composio Tool Router MCP tools to perform actions.",
    systemPrompt:
      "You are a helpful assistant connected to Composio Tool Router."+
"Use the available tools to answer user queries and perform Mailersend actions." ,
    llm,
    tools,
  });

  return agent;
}

async function chatLoop(agent: ReturnType<typeof createAgent>) {
  const rl = readline.createInterface({ input, output });

  console.log("Type 'quit' or 'exit' to stop.");

  while (true) {
    let userInput: string;

    try {
      userInput = (await rl.question("\nYou: ")).trim();
    } catch {
      console.log("\nAgent: Bye!");
      break;
    }

    if (!userInput) {
      continue;
    }

    const lower = userInput.toLowerCase();
    if (lower === "quit" || lower === "exit") {
      console.log("Agent: Bye!");
      break;
    }

    try {
      process.stdout.write("Agent: ");

      const stream = agent.runStream(userInput);
      let finalResult: any = null;

      for await (const event of stream) {
        // The event.data contains the streamed content
        const data: any = event.data;

        // Check for streaming delta content
        if (data?.delta) {
          process.stdout.write(data.delta);
        }

        // Store final result for fallback
        if (data?.result || data?.message) {
          finalResult = data;
        }
      }

      // If no streaming happened, show the final result
      if (finalResult) {
        const answer =
          finalResult.result ??
          finalResult.message?.content ??
          finalResult.message ??
          "";
        if (answer && typeof answer === "string" && !answer.includes("[object")) {
          process.stdout.write(answer);
        }
      }

      console.log(); // New line after streaming completes
    } catch (err: any) {
      console.error("\nAgent error:", err?.message ?? err);
    }
  }

  rl.close();
}

async function main() {
  try {
    const agent = await buildAgent();
    await chatLoop(agent);
  } catch (err: any) {
    console.error("Failed to start agent:", err?.message ?? err);
    process.exit(1);
  }
}

main();
```

## Conclusion

You've successfully connected Mailersend to LlamaIndex through Composio's Tool Router MCP layer.
Key takeaways:
- Tool Router dynamically exposes Mailersend tools through an MCP endpoint
- LlamaIndex's ReActAgent handles reasoning and orchestration; Composio handles integrations
- The agent becomes more capable without increasing prompt size
- Async Python provides clean, efficient execution of agent workflows
You can easily extend this to other toolkits like Gmail, Notion, Stripe, GitHub, and more by adding them to the toolkits parameter.

## How to build Mailersend MCP Agent with another framework

- [OpenAI Agents SDK](https://composio.dev/toolkits/mailersend/framework/open-ai-agents-sdk)
- [Claude Agent SDK](https://composio.dev/toolkits/mailersend/framework/claude-agents-sdk)
- [Claude Code](https://composio.dev/toolkits/mailersend/framework/claude-code)
- [Claude Cowork](https://composio.dev/toolkits/mailersend/framework/claude-cowork)
- [Codex](https://composio.dev/toolkits/mailersend/framework/codex)
- [OpenClaw](https://composio.dev/toolkits/mailersend/framework/openclaw)
- [Hermes](https://composio.dev/toolkits/mailersend/framework/hermes-agent)
- [CLI](https://composio.dev/toolkits/mailersend/framework/cli)
- [Google ADK](https://composio.dev/toolkits/mailersend/framework/google-adk)
- [LangChain](https://composio.dev/toolkits/mailersend/framework/langchain)
- [Vercel AI SDK](https://composio.dev/toolkits/mailersend/framework/ai-sdk)
- [Mastra AI](https://composio.dev/toolkits/mailersend/framework/mastra-ai)
- [CrewAI](https://composio.dev/toolkits/mailersend/framework/crew-ai)

## Related Toolkits

- [Gmail](https://composio.dev/toolkits/gmail) - Gmail is Google's email service with powerful spam protection, search, and G Suite integration. It keeps your inbox organized and makes communication fast and reliable.
- [Outlook](https://composio.dev/toolkits/outlook) - Outlook is Microsoft's email and calendaring platform for unified communications and scheduling. It helps users stay organized with powerful email, contacts, and calendar management.
- [Slack](https://composio.dev/toolkits/slack) - Slack is a channel-based messaging platform for teams and organizations. It helps people collaborate in real time, share files, and connect all their tools in one place.
- [Gong](https://composio.dev/toolkits/gong) - Gong is a platform for video meetings, call recording, and team collaboration. It helps teams capture conversations, analyze calls, and turn insights into action.
- [Microsoft teams](https://composio.dev/toolkits/microsoft_teams) - Microsoft Teams is a collaboration platform that combines chat, meetings, and file sharing within Microsoft 365. It keeps distributed teams connected and productive through seamless virtual communication.
- [Slackbot](https://composio.dev/toolkits/slackbot) - Slackbot is a conversational automation tool for Slack that handles reminders, notifications, and automated responses. It boosts team productivity by streamlining onboarding, answering FAQs, and managing timely alerts—all right inside Slack.
- [2chat](https://composio.dev/toolkits/_2chat) - 2chat is an API platform for WhatsApp and multichannel text messaging. It streamlines chat automation, group management, and real-time messaging for developers.
- [Agent mail](https://composio.dev/toolkits/agent_mail) - Agent mail provides AI agents with dedicated email inboxes for sending, receiving, and managing emails. It empowers agents to communicate autonomously with people, services, and other agents—no human intervention needed.
- [Basecamp](https://composio.dev/toolkits/basecamp) - Basecamp is a project management and team collaboration tool by 37signals. It helps teams organize tasks, share files, and communicate efficiently in one place.
- [Chatwork](https://composio.dev/toolkits/chatwork) - Chatwork is a team communication platform with group chats, file sharing, and task management. It helps businesses boost collaboration and streamline productivity.
- [Clickmeeting](https://composio.dev/toolkits/clickmeeting) - ClickMeeting is a cloud-based platform for running online meetings and webinars. It helps businesses and individuals host, manage, and engage virtual audiences with ease.
- [Confluence](https://composio.dev/toolkits/confluence) - Confluence is Atlassian's team collaboration and knowledge management platform. It helps your team organize, share, and update documents and project content in one secure workspace.
- [Dailybot](https://composio.dev/toolkits/dailybot) - DailyBot streamlines team collaboration with chat-based standups, reminders, and polls. It keeps work flowing smoothly in your favorite messaging platforms.
- [Dialmycalls](https://composio.dev/toolkits/dialmycalls) - Dialmycalls is a mass notification service for sending voice and text messages to contacts. It helps teams and organizations quickly broadcast urgent alerts and updates.
- [Dialpad](https://composio.dev/toolkits/dialpad) - Dialpad is a cloud-based business phone and contact center system for teams. It unifies voice, video, messaging, and meetings across your devices.
- [Discord](https://composio.dev/toolkits/discord) - Discord is a real-time messaging and VoIP platform for communities and teams. It lets users chat, share media, and collaborate across public and private channels.
- [Discordbot](https://composio.dev/toolkits/discordbot) - Discordbot is an automation tool for Discord servers that handles moderation, messaging, and user engagement. It helps communities run smoothly by automating routine and complex tasks.
- [Echtpost](https://composio.dev/toolkits/echtpost) - Echtpost is a secure digital communication platform for encrypted document and message exchange. It ensures confidential data stays private and protected during transmission.
- [Egnyte](https://composio.dev/toolkits/egnyte) - Egnyte is a cloud-based platform for secure file sharing, storage, and governance. It helps teams collaborate efficiently while maintaining data compliance and security.
- [Google Meet](https://composio.dev/toolkits/googlemeet) - Google Meet is a secure video conferencing platform for virtual meetings, chat, and screen sharing. It helps teams connect, collaborate, and communicate seamlessly from anywhere.

## Frequently Asked Questions

### What are the differences in Tool Router MCP and Mailersend MCP?

With a standalone Mailersend MCP server, the agents and LLMs can only access a fixed set of Mailersend tools tied to that server. However, with the Composio Tool Router, agents can dynamically load tools from Mailersend and many other apps based on the task at hand, all through a single MCP endpoint.

### Can I use Tool Router MCP with LlamaIndex?

Yes, you can. LlamaIndex 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 Mailersend tools.

### Can I manage the permissions and scopes for Mailersend while using Tool Router?

Yes, absolutely. You can configure which Mailersend 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 Mailersend data and credentials are handled as safely as possible.

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