MCP Server

​

Overview

​

What can Retell’s MCP server do?

• Agents: create, update, publish, list, and fetch agent versions.
• Calls: create phone/web calls, fetch call details, list calls, delete calls, update call metadata, run QA and review.
• Phone numbers: import, provision, list, and fetch phone numbers.
• Knowledge base: create KBs, attach sources, remove sources, list KBs.
• Voices: list voices, clone voices, search community voices.
• Chats: create chats, create chat agents, end chats, update chat metadata.
• Testing & QA: create test cases, run tests, list/rerun QA, submit scores.
• Alerts & webhooks: create/list alert rules, list incidents, test webhooks.

​

How it works

• Runtime: MCP clients connect to a hosted (remote) MCP endpoint over Streamable HTTP, authenticate with your Retell API key, then call tools.
• Tool discovery: your MCP client can list available tools (via tools/list), including each tool’s name, description, and JSON input schema.

​

Prerequisites

• A Retell API key (get one here)
• An MCP client (Cursor, Claude Desktop, Claude Code, etc.)
• Retell MCP server URL: https://retell.stlmcp.com

Authorization: Bearer <RETELL_API_KEY>

​

Setup

• URL: https://retell.stlmcp.com
• Headers: Authorization: Bearer <RETELL_API_KEY>

​

Client setup

{
  "mcpServers": {
    "retell": {
      "url": "https://retell.stlmcp.com",
      "headers": {
        "Authorization": "Bearer <RETELL_API_KEY>"
      }
    }
  }
}

{
  "mcpServers": {
    "retell": {
      "url": "https://retell.stlmcp.com",
      "headers": {
        "Authorization": "Bearer <RETELL_API_KEY>"
      }
    }
  }
}

claude mcp add --transport http retell https://retell.stlmcp.com \
  --header "Authorization: Bearer <RETELL_API_KEY>"

[mcp_servers.retell]
url = "https://retell.stlmcp.com"
bearer_token_env_var = "RETELL_API_KEY"

export RETELL_API_KEY="<RETELL_API_KEY>"

​

Prompt examples

• “List my agents and summarize what each one does.”
• “Create a new agent for inbound sales qualification and publish it.”
• “Show me the last 20 calls and flag any with low QA scores.”
• “Create a knowledge base and attach these sources, then update my agent to use it.”
• “Import this phone number and assign it to my agent.”
• “Rerun QA on this call and summarize the failure reasons.”

​

Security considerations

​

Recommendations

• Use least privilege: create keys with the minimum permissions needed.
• Keep keys out of prompts: store API keys in client secrets/settings, never paste them into chat.
• Prefer read-first workflows: fetch the current resource before you update or delete it.
• Review destructive actions: tools like delete and publish should be gated by explicit user intent.
• Be careful with PII: call logs and transcripts may contain sensitive data — avoid sending full transcripts back to the model if you don’t need them.
• Use non-production data when possible: if you’re exploring agent behavior or testing workflows, prefer development/sandbox environments.

​

Troubleshooting

​

Feedback