# Send SMS from a LangChain agent

Source: https://jointextkit.com/integrations/langchain
Index: https://jointextkit.com/llms.txt

Load TextKit's tools into a LangChain agent through LangChain's MCP adapter,
in Python or JavaScript, so the agent can send texts and read back delivery.

## 1. Get a test key

Create a test key on the [API keys](/console) page of the console. It starts
`ssms_sk_test_`, runs everything in the [sandbox](/docs/sandbox), and texts no
real phone except your own verified one. Put it in your environment as
`TEXTKIT_API_KEY`:

```bash
export TEXTKIT_API_KEY=ssms_sk_test_...
```

## 2. Connect the MCP server (Python)

Since LangChain 1.4 the adapter ships in `langchain.mcp` and is built on
FastMCP. A FastMCP `Client` with `auth` set to your key sends it as
`Authorization: Bearer`:

```bash
pip install "langchain[mcp]"
```

```python
import asyncio
import os

from fastmcp.client import Client
from langchain.agents import create_agent
from langchain.mcp import MCPAdapter


async def main():
    client = Client("https://mcp.jointextkit.com", auth=os.environ["TEXTKIT_API_KEY"])
    async with MCPAdapter(client) as adapter:
        tools = await adapter.list_tools()
        agent = create_agent("claude-sonnet-5", tools)
        result = await agent.ainvoke(
            {"messages": [{"role": "user", "content": 'Text +15005550006 "Your order shipped."'}]}
        )
        print(result["messages"][-1].content)


asyncio.run(main())
```

Install your model provider's LangChain package alongside it. LangChain marks
the `langchain.mcp` namespace as beta.

## Or in JavaScript

```bash
npm install langchain @langchain/mcp-adapters@^2.0.0 @langchain/core @langchain/langgraph
```

```typescript
import { MCPAdapter } from '@langchain/mcp-adapters';
import { createAgent } from 'langchain';

const adapter = new MCPAdapter({
  servers: {
    textkit: {
      url: 'https://mcp.jointextkit.com',
      headers: { Authorization: `Bearer ${process.env.TEXTKIT_API_KEY}` },
    },
  },
});

try {
  const tools = await adapter.listTools();
  const agent = createAgent({ model: 'claude-sonnet-5', tools });
  const result = await agent.invoke({
    messages: [{ role: 'user', content: 'Text +15005550006 "Your order shipped."' }],
  });
  console.log(result.messages.at(-1)?.content);
} finally {
  await adapter.close();
}
```

A `url` defaults to Streamable HTTP, which is what the TextKit server speaks.
The server exposes 142 tools: messages, verification, numbers, contacts,
segments, broadcasts, automations and account reads. Each one is a single API
call with your key, so the key's scopes, rate limits and send checks apply
unchanged. The full list is on the [MCP server](/docs/mcp) page.

## 3. Check the sandbox run

`+15005550006` is a sandbox number that always ends `delivered`, so the
agent's tool call returns a message with an id starting `msg_` and nothing
reaches a phone. The message also shows in the console's message log, tagged
`Test`. Ask for a text to your own number instead and, once that number is
verified under Settings, it really arrives (up to 10 a day, ending
"- via TextKit sandbox").

## Go live

Swap the test key for a live one (`ssms_sk_live_`). A live text needs a
number on your account: [buy one](/docs/numbers) and
[register your use case](/docs/compliance) with the carriers. When the
account has one number, `from` is optional and the text goes out from it.
To limit what an agent can do with a live key, give it one with only the
[scopes](/docs/authentication) it needs.

## Sources

- [LangChain: MCP (Python)](https://docs.langchain.com/oss/python/langchain/mcp)
- [LangChain: MCP authentication (Python)](https://docs.langchain.com/oss/python/langchain/mcp/auth)
- [LangChain: MCP (JavaScript)](https://docs.langchain.com/oss/javascript/langchain/mcp)
- [LangChain: MCP authentication (JavaScript)](https://docs.langchain.com/oss/javascript/langchain/mcp/auth)