LangChain Tools

The langchain-kudosity package gives your LangChain.js agent tools to send SMS, MMS, and RCS through Kudosity. Hand the tools to an agent, and it can text a customer whenever its logic decides to — an appointment reminder after a booking, a delivery update, a follow-up when a lead goes quiet.

The package is open source under the MIT licence at github.com/kudosity/langchain-kudosity.

Install

npm install langchain-kudosity @langchain/core

The package works with @langchain/core 0.3 and 1.x.

Before you begin

You need:

• A Kudosity account. Sign up if you do not have one.
• Your API key, from the dashboard under Developers > API Settings.
• A registered sender: a virtual number or alphanumeric sender ID for SMS and MMS, and a registered RCS agent ID for RCS.

Set your API key as an environment variable:

export KUDOSITY_API_KEY="your_api_key"

Available tools

Each tool returns the message id and status as JSON, so your agent can match the send against delivery webhooks. When a call fails, the tool returns the API's validation detail — every failed field at once — as JSON instead of throwing, so the agent can correct its input and retry.

Use a tool directly

import { KudositySendSms } from "langchain-kudosity";

const sendSms = new KudositySendSms({
  // a virtual number on your account, or an alphanumeric sender ID (max 11 chars)
  defaultSender: "61481074185",
});

const result = await sendSms.invoke({
  recipient: "61491570156",
  message: "Your appointment is tomorrow at 10am. Reply STOP to opt out.",
});
// → {"id":"2d2c8fb6-…","status":"queued","recipient":"61491570156",…}

Hand the tools to an agent

import { createAgent } from "langchain";
import {
  KudositySendSms,
  KudositySendMms,
  KudositySendRcs,
} from "langchain-kudosity";

const tools = [
  new KudositySendSms({ defaultSender: "61481074185" }),
  new KudositySendMms({ defaultSender: "61481074185" }),
  new KudositySendRcs({
    defaultSender: "YourAgentId", // a registered RCS agent ID, not a phone number
    defaultFallbackSender: "61481074185",
  }),
];

const agent = createAgent({ model: "anthropic:claude-sonnet-5", tools });

await agent.invoke({
  messages: [
    { role: "user", content: "Text 61491570156 that their delivery arrives Thursday." },
  ],
});

The model supplies the recipient and message. The sender comes from your configuration by default, so the model cannot invent one — it can only override it with another sender you have registered.

RCS: two things to get right

• The RCS sender is a registered RCS agent ID, never a phone number. Registration is not part of the API — see the RCS agent registration process, then use the agent ID here.
• Include an SMS fallback on almost every send. Not every handset can receive RCS. The tool's input schema prompts the model to supply sms_fallback_message; the fallback sender stays in your configuration (defaultFallbackSender), so the model never picks the number.

Configuration reference

Next steps

• Agent Skills — teach coding agents how the whole API behaves, including WhatsApp and contact lists
• Kudosity MCP server — the same capability for MCP-compatible clients
• Send messages from AI agents — runnable examples for every channel