How to integrate Retellai MCP with OpenAI Agents SDK

This guide walks you through connecting Retellai to the OpenAI Agents SDK using the Composio tool router. By the end, you'll have a working Retellai agent that can list all phone numbers linked to your account, retrieve call details for a specific agent this week, buy a new phone number with area code 415 through natural language commands. This guide will help you understand how to give your OpenAI Agents SDK agent real control over a Retellai account through Composio's Retellai MCP server. Before we dive in, let's take a quick look at the key ideas and tools involved.

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RetellAI is a platform for capturing calls and transcripts, centralizing business conversations. It helps teams analyze interactions and extract insights to improve customer experience.

67 Tools

Introduction

This guide walks you through connecting Retellai to the OpenAI Agents SDK using the Composio tool router. By the end, you'll have a working Retellai agent that can list all phone numbers linked to your account, retrieve call details for a specific agent this week, buy a new phone number with area code 415 through natural language commands.

This guide will help you understand how to give your OpenAI Agents SDK agent real control over a Retellai account through Composio's Retellai MCP server.

Before we dive in, let's take a quick look at the key ideas and tools involved.

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TL;DR

Here's what you'll learn:
  • Get and set up your OpenAI and Composio API keys
  • Install the necessary dependencies
  • Initialize Composio and create a Tool Router session for Retellai
  • Configure an AI agent that can use Retellai as a tool
  • Run a live chat session where you can ask the agent to perform Retellai operations

What is OpenAI Agents SDK?

The OpenAI Agents SDK is a lightweight framework for building AI agents that can use tools and maintain conversation state. It provides a simple interface for creating agents with hosted MCP tool support.

Key features include:

  • Hosted MCP Tools: Connect to external services through hosted MCP endpoints
  • SQLite Sessions: Persist conversation history across interactions
  • Simple API: Clean interface with Agent, Runner, and tool configuration
  • Streaming Support: Real-time response streaming for interactive applications

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

The Retellai MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to your Retellai account. It provides structured and secure access to your call records, phone numbers, and conversation transcripts, so your agent can perform actions like retrieving call details, managing phone numbers, initiating outbound calls, and analyzing voice data on your behalf.

  • Retrieve and analyze call records: Your agent can fetch detailed call logs, filter by agent or time, and surface insights from past conversations.
  • Initiate outbound and web-based calls: Easily direct your agent to start new phone or web calls between specific numbers or agents, supporting various business workflows.
  • Manage phone numbers and assignments: Buy, update, or delete phone numbers, and bind them to agents for streamlined inbound and outbound call handling.
  • Access and review call transcripts and details: Let your agent drill down into specific calls, pulling transcripts and metadata for compliance, training, or analytics.
  • Explore and configure voice settings: Fetch detailed information about available voice options, including provider, accent, gender, and preview audio for customization of call experiences.

What is the Composio tool router, and how does it fit here?

What is Composio SDK?

Composio's Composio SDK helps agents find the right tools for a task at runtime. You can plug in multiple toolkits (like Gmail, HubSpot, and GitHub), and the agent will identify the relevant app and action to complete multi-step workflows. This can reduce token usage and improve the reliability of tool calls. Read more here: Getting started with Composio SDK

The tool router generates a secure MCP URL that your agents can access to perform actions.

How the Composio SDK works

The Composio SDK follows a three-phase workflow:

  1. Discovery: Searches for tools matching your task and returns relevant toolkits with their details.
  2. Authentication: Checks for active connections. If missing, creates an auth config and returns a connection URL via Auth Link.
  3. Execution: Executes the action using the authenticated connection.

Step-by-step Guide

Step by step09 STEPS
1

Prerequisites

Before starting, make sure you have:
  • Composio API Key and OpenAI API Key
  • Primary know-how of OpenAI Agents SDK
  • A live Retellai project
  • Some knowledge of Python or Typescript
2

Getting API Keys for OpenAI and Composio

OpenAI API Key
  • Go to the OpenAI dashboard and create an API key. You'll need credits to use the models, or you can connect to another model provider.
  • Keep the API key safe.
Composio API Key
3

Install dependencies

npm install @composio/openai-agents @openai/agents dotenv

Install the Composio SDK and the OpenAI Agents SDK.

4

Set up environment variables

bash
OPENAI_API_KEY=sk-...your-api-key
COMPOSIO_API_KEY=your-api-key
USER_ID=composio_user@gmail.com

Create a .env file and add your OpenAI and Composio API keys.

5

Import dependencies

import 'dotenv/config';
import { Composio } from '@composio/core';
import { OpenAIAgentsProvider } from '@composio/openai-agents';
import { Agent, hostedMcpTool, run, OpenAIConversationsSession } from '@openai/agents';
import * as readline from 'readline';
What's happening:
  • You're importing all necessary libraries.
  • The Composio and OpenAIAgentsProvider classes are imported to connect your OpenAI agent to Composio tools like Retellai.
6

Set up the Composio instance

dotenv.config();

const composioApiKey = process.env.COMPOSIO_API_KEY;
const userId = process.env.USER_ID;

if (!composioApiKey) {
  throw new Error('COMPOSIO_API_KEY is not set. Create a .env file with COMPOSIO_API_KEY=your_key');
}
if (!userId) {
  throw new Error('USER_ID is not set');
}

// Initialize Composio
const composio = new Composio({
  apiKey: composioApiKey,
  provider: new OpenAIAgentsProvider(),
});
What's happening:
  • dotenv.config() loads your .env file so COMPOSIO_API_KEY and USER_ID are available as environment variables.
  • Creating a Composio instance using the API Key and OpenAIAgentsProvider class.
7

Create a Tool Router session

// Create Tool Router session for Retellai
const session = await composio.create(userId as string, {
  toolkits: ['retellai'],
});
const mcpUrl = session.mcp.url;

What is happening:

  • You give the Tool Router the user id and the toolkits you want available. Here, it is only retellai.
  • The router checks the user's Retellai connection and prepares the MCP endpoint.
  • The returned session.mcp.url is the MCP URL that your agent will use to access Retellai.
  • This approach keeps things lightweight and lets the agent request Retellai tools only when needed during the conversation.
8

Configure the agent

// Configure agent with MCP tool
const agent = new Agent({
  name: 'Assistant',
  model: 'gpt-5',
  instructions:
    'You are a helpful assistant that can access Retellai. Help users perform Retellai operations through natural language.',
  tools: [
    hostedMcpTool({
      serverLabel: 'tool_router',
      serverUrl: mcpUrl,
      headers: { 'x-api-key': composioApiKey },
      requireApproval: 'never',
    }),
  ],
});
What's happening:
  • We're creating an Agent instance with a name, model (gpt-5), and clear instructions about its purpose.
  • The agent's instructions tell it that it can access Retellai and help with queries, inserts, updates, authentication, and fetching database information.
  • The tools array includes a hostedMcpTool that connects to the MCP server URL we created earlier.
  • The headers object includes the Composio API key for secure authentication with the MCP server.
  • requireApproval: 'never' means the agent can execute Retellai operations without asking for permission each time, making interactions smoother.
9

Start chat loop and handle conversation

// Keep conversation state across turns
const conversationSession = new OpenAIConversationsSession();

// Simple CLI
const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout,
  prompt: 'You: ',
});

console.log('\nComposio Tool Router session created.');
console.log('\nChat started. Type your requests below.');
console.log("Commands: 'exit', 'quit', or 'q' to end\n");

try {
  const first = await run(agent, 'What can you help me with?', { session: conversationSession });
  console.log(`Assistant: ${first.finalOutput}\n`);
} catch (e) {
  console.error('Error:', e instanceof Error ? e.message : e, '\n');
}

rl.prompt();

rl.on('line', async (userInput) => {
  const text = userInput.trim();

  if (['exit', 'quit', 'q'].includes(text.toLowerCase())) {
    console.log('Goodbye!');
    rl.close();
    process.exit(0);
  }

  if (!text) {
    rl.prompt();
    return;
  }

  try {
    const result = await run(agent, text, { session: conversationSession });
    console.log(`\nAssistant: ${result.finalOutput}\n`);
  } catch (e) {
    console.error('Error:', e instanceof Error ? e.message : e, '\n');
  }

  rl.prompt();
});

rl.on('close', () => {
  console.log('\n👋 Session ended.');
  process.exit(0);
});
What's happening:
  • The program prints a session URL that you visit to authorize Retellai.
  • After authorization, the chat begins.
  • Each message you type is processed by the agent using run().
  • The responses are printed to the console.
  • Typing exit, quit, or q cleanly ends the chat.

Complete Code

Here's the complete code to get you started with Retellai and OpenAI Agents SDK:

import 'dotenv/config';
import { Composio } from '@composio/core';
import { OpenAIAgentsProvider } from '@composio/openai-agents';
import { Agent, hostedMcpTool, run, OpenAIConversationsSession } from '@openai/agents';
import * as readline from 'readline';

const composioApiKey = process.env.COMPOSIO_API_KEY;
const userId = process.env.USER_ID;

if (!composioApiKey) {
  throw new Error('COMPOSIO_API_KEY is not set. Create a .env file with COMPOSIO_API_KEY=your_key');
}
if (!userId) {
  throw new Error('USER_ID is not set');
}

// Initialize Composio
const composio = new Composio({
  apiKey: composioApiKey,
  provider: new OpenAIAgentsProvider(),
});

async function main() {
  // Create Tool Router session
  const session = await composio.create(userId as string, {
    toolkits: ['retellai'],
  });
  const mcpUrl = session.mcp.url;

  // Configure agent with MCP tool
  const agent = new Agent({
    name: 'Assistant',
    model: 'gpt-5',
    instructions:
      'You are a helpful assistant that can access Retellai. Help users perform Retellai operations through natural language.',
    tools: [
      hostedMcpTool({
        serverLabel: 'tool_router',
        serverUrl: mcpUrl,
        headers: { 'x-api-key': composioApiKey },
        requireApproval: 'never',
      }),
    ],
  });

  // Keep conversation state across turns
  const conversationSession = new OpenAIConversationsSession();

  // Simple CLI
  const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
    prompt: 'You: ',
  });

  console.log('\nComposio Tool Router session created.');
  console.log('\nChat started. Type your requests below.');
  console.log("Commands: 'exit', 'quit', or 'q' to end\n");

  try {
    const first = await run(agent, 'What can you help me with?', { session: conversationSession });
    console.log(`Assistant: ${first.finalOutput}\n`);
  } catch (e) {
    console.error('Error:', e instanceof Error ? e.message : e, '\n');
  }

  rl.prompt();

  rl.on('line', async (userInput) => {
    const text = userInput.trim();

    if (['exit', 'quit', 'q'].includes(text.toLowerCase())) {
      console.log('Goodbye!');
      rl.close();
      process.exit(0);
    }

    if (!text) {
      rl.prompt();
      return;
    }

    try {
      const result = await run(agent, text, { session: conversationSession });
      console.log(`\nAssistant: ${result.finalOutput}\n`);
    } catch (e) {
      console.error('Error:', e instanceof Error ? e.message : e, '\n');
    }

    rl.prompt();
  });

  rl.on('close', () => {
    console.log('\nSession ended.');
    process.exit(0);
  });
}

main().catch((err) => {
  console.error('Fatal error:', err);
  process.exit(1);
});

Conclusion

This was a starter code for integrating Retellai MCP with OpenAI Agents SDK to build a functional AI agent that can interact with Retellai.

Key features:

  • Hosted MCP tool integration through Composio's Tool Router
  • SQLite session persistence for conversation history
  • Simple async chat loop for interactive testing
You can extend this by adding more toolkits, implementing custom business logic, or building a web interface around the agent.
TOOLS

Supported Tools

Every Retellai action and event your agent gets out of the box.

Add community voice

Add a community voice from ElevenLabs to your Retell voice library.

Add sources to knowledge base

Tool to add sources (documents, URLs, text) to an existing knowledge base in Retell AI.

Buy a new phone number bind agents

This endpoint allows purchasing a new phone number with a specified area code and binding it to designated agents for inbound and outbound calls.

Create Voice AI Agent

Create a new voice AI agent with specified configuration.

Create a new outbound phone call

Initiate an outbound call by POST to '/v2/create-phone-call'.

Create a new web call

The /v2/create-web-call endpoint creates a web call with a unique agent ID, returning call details like type, token, call ID, and status in JSON format, with a 201 response.

Create Batch Test

Tool to create a batch test job that runs multiple test cases against an agent.

Create a new chat session

Tool to create a new chat session with a chat agent.

Create a new chat agent

Create a new chat agent with specified configuration.

Create chat completion

Tool to create a chat completion for an existing chat session, generating the agent's response to a user message.

Create conversation flow

Create a new Conversation Flow that can be attached to an agent for response generation.

Create conversation flow component

Creates a new shared conversation flow component at POST '/create-conversation-flow-component'.

Create a new knowledge base

Tool to create a new knowledge base in Retell AI with texts, files, and URLs.

Create Retell LLM Response Engine

Create a new Retell LLM Response Engine that can be attached to an agent.

Create Test Case Definition

Tool to create a test case definition for agent QA testing in Retell AI.

Delete agent

Deletes an existing agent by its unique identifier.

Delete call

Delete a specific call and its associated data by call ID.

Delete chat agent

Delete an existing chat agent by its unique identifier.

Delete conversation flow

Delete a conversation flow and all its versions.

Delete conversation flow component

Delete a shared conversation flow component.

Delete knowledge base

Delete an existing knowledge base by its unique identifier.

Delete knowledge base source

Delete an existing source from a knowledge base.

Delete phone number

Tool to delete an existing phone number from Retell AI.

Delete Retell LLM

Delete an existing Retell LLM Response Engine by its unique identifier.

Delete test case definition

Delete a test case definition by its unique identifier.

End chat

Tool to end an active chat session.

Retrieve details of a specific agent

Retrieve details of a specific agent by its unique identifier.

Get agent versions

Tool to retrieve all versions of a specific agent.

Get batch test

Retrieve details and results of a specific batch test job.

Get chat details

Tool to retrieve details of a specific chat session by chat ID.

Retrieve details of a specific chat agent

Retrieve details of a specific chat agent by its unique identifier.

Get all versions of a chat agent

Retrieve all versions of a specific chat agent by its unique identifier.

Get concurrency

Retrieves the current concurrency and concurrency limits for the organization.

Get Conversation Flow

Retrieve details of a specific Conversation Flow by its ID.

Get conversation flow component

Retrieves a shared conversation flow component by its unique identifier.

Get knowledge base

Retrieve details of a specific knowledge base by its unique identifier.

Retrieve details of a specific Retell LLM

Retrieve details of a specific Retell LLM Response Engine by its unique identifier.

Import phone number

Tool to import a phone number from custom telephony and bind agents to it.

List agents

Retrieves a list of all agents associated with the account.

List all chats

Tool to retrieve a list of all chats associated with the account.

List all phone numbers

Retrieves a list of all phone numbers associated with the account.

List batch tests

Tool to list batch test jobs for a response engine.

List chat agents

Tool to retrieve a list of all chat agents associated with the account.

List conversation flow components

Retrieves a list of all shared conversation flow components.

List conversation flows

Tool to list all conversation flows that can be attached to an agent.

List knowledge bases

Tool to retrieve all knowledge bases associated with the account.

List Retell LLMs

Tool to list all Retell LLM Response Engines that can be attached to an agent.

List test case definitions

Tool to list test case definitions for a response engine (Retell LLM or Conversation Flow).

List test runs

Tool to list all test case jobs (test runs) for a batch test job.

List voices

List all voices available to the user.

Publish agent

Publishes the latest version of the agent and creates a new draft agent with a newer version.

Publish chat agent

Publishes the latest version of the chat agent and creates a new draft chat agent with a newer version.

Register phone call

Register a phone call for custom telephony integration with Retell AI.

Retrieve call details

Tool to retrieve call details with filtering options.

Retrieve call details by id

Retrieve call details by ID for web/phone calls, including type, agent ID, status, timestamps, and web access token; covering responses from success to server errors.

Retrieve phone number details

Tool to retrieve details of a specific phone number from Retell AI.

Retrieve details of a specific voice

Tool to retrieve details of a specific voice by its voice_id.

Search community voice

Search for community voices from voice providers.

Update agent

Update an existing agent's latest draft version.

Update call

Update an active call's parameters such as metadata, dynamic variables, or data storage settings.

Update chat agent

Update an existing chat agent configuration.

Update chat metadata

Tool to update metadata and sensitive data storage settings for an existing chat.

Update conversation flow

Update an existing conversation flow configuration.

Update conversation flow component

Update an existing shared conversation flow component by its ID.

Update phone number configuration

Update agent bound to a purchased phone number.

Update Retell LLM Response Engine

Update an existing Retell LLM Response Engine by its unique identifier.

Update test case definition

Update a test case definition for agent testing.

FRAMEWORKS

How to build Retellai MCP Agent with another framework

Claude Agent SDK logo

Claude Agent SDK

Use Retellai MCP with Claude Agent SDK

Claude Code logo

Claude Code

Use Retellai MCP with Claude Code

Claude Cowork logo

Claude Cowork

Use Retellai MCP with Claude Cowork

Codex logo

Codex

Use Retellai MCP with Codex

OpenClaw logo

OpenClaw

Use Retellai MCP with OpenClaw

Hermes logo

Hermes

Use Retellai MCP with Hermes

CLI logo

CLI

Use Retellai MCP with CLI

Google ADK logo

Google ADK

Use Retellai MCP with Google ADK

LangChain logo

LangChain

Use Retellai MCP with LangChain

Vercel AI SDK logo

Vercel AI SDK

Use Retellai MCP with Vercel AI SDK

Mastra AI logo

Mastra AI

Use Retellai MCP with Mastra AI

LlamaIndex logo

LlamaIndex

Use Retellai MCP with LlamaIndex

CrewAI logo

CrewAI

Use Retellai MCP with CrewAI

FAQ

Frequently asked questions

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

Yes, you can. OpenAI Agents SDK 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 Retellai tools.

Yes, absolutely. You can configure which Retellai 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.

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 Retellai data and credentials are handled as safely as possible.

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Co-founder, Slashy

A lot of students tell us that the moment their connected tools start talking to each other inside Opennote feels almost magical. The agent just knows them, and it's immensely helped keep new users on the platform.

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Co-founder, Opennote

We chose Composio over Pipedream because it delivered depth where it mattered — niche tools and tricky edge cases other platforms simply ignored. That gave us confidence to scale without compromising.

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CEO, Zams

As a solo builder, shipping fast is life or death. The only way I can outcompete incumbents is by outmanoeuvring them. Getting bogged down managing agent auth would have been a death sentence.

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Founder, Extra Thursday

Before Composio, adding tool integrations was slow and resource-intensive. Each one could take weeks of engineering time, and maintaining them meant constantly keeping up with API changes.

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Founder & CEO, SwarmZero

With hands-on help from their founder, we integrated Gmail and Google Drive in just 30 minutes. This level of personal support and commitment is exactly what startups should strive for.

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Co-Founder, Ingram Technologies