One endpoint. Any MCP SDK.

0 Get a key (your agent can do this)

POST /api/v1/signup needs no key and no card. Your agent can call it itself; a six-digit code goes to your email. The key is free and shown once. A real phone number turns on with a paid plan: $2 for your first week, then Kai Backup $10/mo. Full request and response shapes are in the homepage quickstart.

curl -X POST https://www.kaicalls.com/api/v1/signup \
  -H "Content-Type: application/json" \
  -d '{
    "business_name": "YOUR BUSINESS",
    "email": "you@yourdomain.com",
    "activation_mode": "otp",
    "api_key_scopes": ["agents:read", "calls:read", "calls:write"]
  }'
# → { "status": "otp_sent", "challenge_id": "..." }
# Send the same body again with "challenge_id" and the emailed "otp_code"
# → one-time api_key (kc_live_...) and agent_id

a MCP client config

Paste into any MCP client that takes an mcpServers block (Claude Desktop, Cursor, a project .mcp.json). Some clients spell the type streamable-http; the URL and header are the same.

{
  "mcpServers": {
    "callmcp": {
      "type": "http",
      "url": "https://callmcp.ai/mcp",
      "headers": { "Authorization": "Bearer kc_live_..." }
    }
  }
}

b Claude Code

One line. Then run /mcp in Claude Code to confirm the tools loaded.

claude mcp add --transport http callmcp https://callmcp.ai/mcp \
  --header "Authorization: Bearer kc_live_..."

c TypeScript

The official @modelcontextprotocol/sdk with StreamableHTTPClientTransport. Run it as an ES module (top-level await).

// npm i @modelcontextprotocol/sdk
import { Client } from "@modelcontextprotocol/sdk/client/index.js";
import { StreamableHTTPClientTransport } from "@modelcontextprotocol/sdk/client/streamableHttp.js";

const transport = new StreamableHTTPClientTransport(new URL("https://callmcp.ai/mcp"), {
  requestInit: { headers: { Authorization: `Bearer ${process.env.CALLMCP_API_KEY}` } },
});

const client = new Client({ name: "my-agent", version: "1.0.0" });
await client.connect(transport);

const result = await client.callTool({
  name: "make_call",
  arguments: {
    agent_id: "AGENT_ID_FROM_SIGNUP",
    to: "+1YOURCELL",
    context: "Test call: introduce yourself and confirm this line works",
    idempotency_key: "first-test-call-001",
  },
});
console.log(result.structuredContent ?? result.content);
await client.close();

d Python

The official mcp package. httpx2 is installed with it and carries the auth header.

# pip install mcp   (written against mcp 2.3.0)
import asyncio, os

import httpx2
from mcp import ClientSession
from mcp.client.streamable_http import streamable_http_client


async def main() -> None:
    headers = {"Authorization": f"Bearer {os.environ['CALLMCP_API_KEY']}"}
    async with httpx2.AsyncClient(headers=headers, timeout=60) as http:
        async with streamable_http_client("https://callmcp.ai/mcp", http_client=http) as (read, write):
            async with ClientSession(read, write) as session:
                await session.initialize()
                result = await session.call_tool("make_call", {
                    "agent_id": "AGENT_ID_FROM_SIGNUP",
                    "to": "+1YOURCELL",
                    "context": "Test call: introduce yourself and confirm this line works",
                    "idempotency_key": "first-test-call-001",
                })
                print(result.structuredContent or result.content)


asyncio.run(main())

On mcp 1.x (checked on 1.30.0) the transport is streamablehttp_client(url, headers=headers) and it yields (read, write, get_session_id).