Retell AI - Model Context Protocol (MCP) Server

A fully-featured, official-grade Model Context Protocol (MCP) server that provides complete programmatic access to the Retell AI platform.

This MCP server achieves 100% parity with the Retell Node.js SDK, exposing 60 specific tools allowing LLM-powered assistants (like Claude Desktop, Cursor, and Codex) to autonomously build, configure, and operate end-to-end voice and text agents.

Capabilities

With this server, your AI assistant can autonomously:

• Design Agents: Create and configure LLM response engines, Conversation Flows, and Chat Agents.

• Provide Memory: Create Knowledge Bases, upload content, and link them to agents for RAG.

• Manage Telephony: Purchase, import, and configure U.S. or international phone numbers.

• Trigger outbound calls & test: Initiate Web calls, Phone calls, SMS chats, and batch tests.

• Monitor: Retrieve transcripts, real-time metrics, live call concurrency, and latency scores.

Everything available in the official SDK is available as an MCP Tool.

Related MCP server: ElevenLabs MCP Server

Installation

Prerequisites

• Node.js 18+

• A Retell AI API Key (from the Retell Dashboard)

Setup

Clone the repository and install dependencies:

git clone https://github.com/sunnysingh100/retell-mcp-server.git
cd retell-mcp-server
npm install
npm run build

Configuration

To use this with an MCP client (such as Claude Desktop or Codex), you must configure it via your client's settings.

Claude Desktop

Edit your claude_desktop_config.json:

{
  "mcpServers": {
    "retell-ai": {
      "command": "node",
      "args": [
        "/absolute/path/to/retell-mcp-server/dist/index.js"
      ],
      "env": {
        "RETELL_API_KEY": "your_retell_api_key_here"
      }
    }
  }
}

Generic Client

Just run the built script with the environment variable set. The server operates over stdio via the standard MCP JSON-RPC protocol.

RETELL_API_KEY="your_api_key" node dist/index.js

Available Tools (60 Total)

The server supports all 14 domain resources of the Retell SDK.

🎙 Voices

• retell_list_voices: List available voices across providers (ElevenLabs, OpenAI, Deepgram, etc).

🧠 LLMs & Knowledge Bases

• retell_list_llms / retell_get_llm / retell_create_llm / retell_update_llm / retell_delete_llm

• retell_list_knowledge_bases / retell_get_knowledge_base / retell_create_knowledge_base / retell_delete_knowledge_base

• retell_add_knowledge_base_sources / retell_delete_knowledge_base_source

🤖 Voice Agents

• retell_list_agents / retell_get_agent / retell_create_agent / retell_update_agent / retell_delete_agent

• retell_get_agent_versions / retell_publish_agent

📱 Phone Numbers

• retell_list_phone_numbers / retell_get_phone_number / retell_create_phone_number

• retell_update_phone_number / retell_delete_phone_number / retell_import_phone_number

📞 Voice Calls

• retell_list_calls / retell_get_call / retell_update_call / retell_delete_call

• Initiate: retell_create_phone_call / retell_create_web_call / retell_register_phone_call

💬 Chat Agents & Sessions

• Agents: retell_list_chat_agents / retell_get_chat_agent / retell_create_chat_agent / retell_update_chat_agent / retell_delete_chat_agent / retell_get_chat_agent_versions / retell_publish_chat_agent

• Sessions: retell_list_chats / retell_get_chat / retell_create_chat / retell_update_chat / retell_create_chat_completion / retell_create_sms_chat / retell_end_chat

🔀 Conversation Flows (Node-based scripting)

• Flows: retell_list_conversation_flows / retell_get_conversation_flow / retell_create_conversation_flow / retell_update_conversation_flow / retell_delete_conversation_flow

• Components: list, get, create, update, delete for reusable conversation flow components.

⚙️ Utilities

• retell_create_batch_call / retell_create_batch_test

• retell_get_concurrency

• retell_get_mcp_tools

Architectural Notes

• Input Validation: Every tool validates its inputs dynamically using strict zod schemas. Invalid arguments return clean, detailed error messages.

• Type Safety: The entire codebase is thoroughly typed against the retell-sdk, eliminating any casting and masking TypeScript errors.

• Standard Protocol Compliance: All expected errors generate an MCP protocol isError: true payload, ensuring the LLM client correctly handles API rejections without crashing.