JustCall MCP Server

The JustCall Model Context Protocol (MCP) Server lets Large Language Models (LLMs) and AI agents make real-world voice calls and send SMS directly through JustCall’s APIs — securely, contextually, and programmatically.

It provides a function-calling interface for conversational AI systems, enabling:

• 📞 AI-powered calling: Let your LLM initiate, manage, or transcribe calls using JustCall.
• 💬 Smart messaging: Allow your AI agent to send or respond to SMS within conversations.
• ⚙️ Seamless integration: Use the MCP standard to connect JustCall’s telephony capabilities with any LLM runtime or orchestration framework.

In short: It gives your LLMs a voice and a phone number — turning chatbots into truly conversational agents.

Claude Desktop Setup

1. Open Claude Desktop and press CMD + , to go to Settings.
2. Click on the Connectors tab.
3. Click on the Add Custom Connector button.
4. Add name as JustCall and Remote Server Url as https://mcp.justcall.host/mcp.
5. Now on JustCall from the Connectors list click on Connect button for JustCall.
6. It will open a JustCall page requesting API key and secret.
7. Get your JustCall API Key & Secret from the JustCall dashboard (https://app.justcall.io/app/developersApiCredentials).
8. Enter the API key and Secret and press Continue, it should redirect back you to Claude.

Claude Web - https://claude.ai

1. Open connectors url in your Browser - https://claude.ai/settings/connectors.
2. Click on the Connectors tab.
3. Click on the Add Custom Connector button.
4. Add name as JustCall and Remote Server Url as https://mcp.justcall.host/mcp.
5. Now on JustCall from the Connectors list click on Connect button for JustCall.
6. It will open a JustCall page requesting API key and secret.
7. Get your JustCall API Key & Secret from the JustCall dashboard (https://app.justcall.io/app/developersApiCredentials).
8. Enter the API key and Secret and press Continue, it should redirect back you to Claude.

Chat GPT (Only available on Plus, Pro, Business and Enterprise)

1. Open connectors url in your Browser - https://chatgpt.com/#settings/Connectors.
2. Click on the Apps & Connectors tab.
3. Ensure developer mode is enabled in advanced settings
4. Click on the Create button.
5. Add name as JustCall and MCP Server Url as https://mcp.justcall.host/mcp. You can skip other fields.
6. Now on JustCall from the Connectors list click on Connect button for JustCall.
7. It will open a JustCall page requesting API key and secret.
8. Get your JustCall API Key & Secret from the JustCall dashboard (https://app.justcall.io/app/developersApiCredentials).
9. Enter the API key and Secret and press Continue, it should redirect back you to Chat GPT.

Remote MCP

To connect to JustCall's MCP server remotely:

Streamable HTTP (Recommended)

The default and recommended way to connect is via Streamable HTTP Transport:

• Connect to https://mcp.justcall.host/mcp from any MCP client using Streamable HTTP Transport
• Include your JustCall API key as a bearer token in the request headers
• Example header: Authorization: Bearer <JUSTCALL_API_KEY>:<JUSTCALL_API_SECRET>

Authentication & Security

The JustCall MCP Server implements OAuth2 authentication for secure access to all endpoints.

OAuth2 Configuration

The server supports OAuth2 authorization with the following features:

• Authorization Endpoint: OAuth2 authorization server metadata is available at /.well-known/oauth-authorization-server
• Grant Type: Authorization code flow with PKCE (Proof Key for Code Exchange)
• Code Challenge Method: S256 (SHA-256)
• Token Authentication: All MCP and SSE endpoints require Bearer token authentication

Protected Endpoints

The following endpoints require valid Bearer token authentication:

• /mcp - Main MCP endpoint
• /sse - Server-Sent Events endpoint
• /sse/message - SSE

... View full README on GitHub