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Retell AI MCP Integration for LangGraph

Connect Retell AI to LangGraph through the local KosmoKrator MCP gateway with scoped tools, credentials, and write policy.

6 functions 4 read 2 write API key auth
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Connect Retell AI to LangGraph

Run KosmoKrator integration calls from LangGraph nodes while preserving local credentials and permissions.

Use a graph node that calls the KosmoKrator CLI for deterministic steps or an MCP client for dynamic tool selection. The gateway is local, scoped to this integration, and starts with --write=deny so LangGraph can inspect read-capable tools without receiving write access by default.

Retell AI MCP Config for LangGraph

Headless CLI calls fit repeatable graph edges; MCP fits exploratory agent nodes.

{
  "mcpServers": {
    "kosmokrator-retell-ai": {
      "type": "stdio",
      "command": "kosmo",
      "args": [
        "mcp:serve",
        "--integration=retell-ai",
        "--write=deny"
      ]
    }
  }
}

Run the Gateway Manually

kosmokrator mcp:serve --integration=retell-ai --write=deny

Why Use KosmoKrator Here

Scoped tools

Expose only Retell AI instead of a broad multi-service tool list.

Local credentials

Reuse credentials already configured for the KosmoKrator CLI and Lua runtime.

Write policy

Start read-only, then opt into ask or allow for trusted workspaces.

Retell AI Tools Visible to LangGraph

LangGraph sees stable MCP tool names generated from the Retell AI integration catalog.

MCP toolSource functionTypeDescription
integration__retell_ai__retell_ai_create_call retell-ai.retell_ai_create_call Write Create a new AI-powered phone call using a Retell AI voice agent. Specify the agent ID and optional metadata to attach context to the call.
integration__retell_ai__retell_ai_get_call retell-ai.retell_ai_get_call Read Retrieve details for a specific phone call by its ID. Returns call status, duration, transcript, and associated metadata.
integration__retell_ai__retell_ai_list_calls retell-ai.retell_ai_list_calls Read List phone calls from Retell AI. Returns call records with status, duration, and metadata. Supports optional filters for agent, status, or date range.
integration__retell_ai__retell_ai_list_agents retell-ai.retell_ai_list_agents Read List all configured voice agents in your Retell AI account. Returns agent IDs, names, voice settings, and other configuration details.
integration__retell_ai__retell_ai_create_agent retell-ai.retell_ai_create_agent Write Create a new voice AI agent in Retell AI. Specify the voice ID and system prompt. Additional options like agent name, language, and behavior settings can be provided.
integration__retell_ai__retell_ai_get_current_user retell-ai.retell_ai_get_current_user Read Retrieve current Retell AI account information, including available agents and account status. Useful for verifying connectivity and understanding account capabilities.

Related Retell AI Pages

Retell AI CLIUse direct JSON commands instead of MCP discovery. Retell AI MCPFull gateway reference and MCP tool names. KosmoKrator for LangGraphClient-level gateway setup.