How to integrate Splitwise MCP with Mastra AI

This guide walks you through connecting Splitwise to Mastra AI using the Composio tool router. By the end, you'll have a working Splitwise agent that can add a new friend using their email, create a dinner expense split equally, list all groups i'm part of through natural language commands. This guide will help you understand how to give your Mastra AI agent real control over a Splitwise account through Composio's Splitwise MCP server. Before we dive in, let's take a quick look at the key ideas and tools involved.

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Splitwise helps you split bills and expenses with friends and family. It makes it easy to track shared costs and settle up, so everyone stays on the same page.

27 Tools

Introduction

This guide walks you through connecting Splitwise to Mastra AI using the Composio tool router. By the end, you'll have a working Splitwise agent that can add a new friend using their email, create a dinner expense split equally, list all groups i'm part of through natural language commands.

This guide will help you understand how to give your Mastra AI agent real control over a Splitwise account through Composio's Splitwise MCP server.

Before we dive in, let's take a quick look at the key ideas and tools involved.

Also integrate Splitwise with

OpenAI Agents SDKClaude Agent SDKClaude CodeClaude CoworkCodexOpenClawHermesCLIGoogle ADKLangChainVercel AI SDKLlamaIndexCrewAI

TL;DR

Here's what you'll learn:
  • Set up your environment so Mastra, OpenAI, and Composio work together
  • Create a Tool Router session in Composio that exposes Splitwise tools
  • Connect Mastra's MCP client to the Composio generated MCP URL
  • Fetch Splitwise tool definitions and attach them as a toolset
  • Build a Mastra agent that can reason, call tools, and return structured results
  • Run an interactive CLI where you can chat with your Splitwise agent

What is Mastra AI?

Mastra AI is a TypeScript framework for building AI agents with tool support. It provides a clean API for creating agents that can use external services through MCP.

Key features include:

  • MCP Client: Built-in support for Model Context Protocol servers
  • Toolsets: Organize tools into logical groups
  • Step Callbacks: Monitor and debug agent execution
  • OpenAI Integration: Works with OpenAI models via @ai-sdk/openai

What is the Splitwise MCP server, and what's possible with it?

The Splitwise MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to your Splitwise account. It provides structured and secure access to your expenses and group data, so your agent can perform actions like creating expenses, adding friends, retrieving categories, and managing your account on your behalf.

  • Expense tracking and creation: Quickly have your agent record new expenses, split bills, or log payments—either between you and friends or within groups.
  • Friend and contact management: Easily add new friends with their email and name, or remove existing friends to keep your network current.
  • Group info and collaboration: Retrieve details about any group you belong to, making it simple to manage shared costs and stay organized with your housemates, travel buddies, or teams.
  • Expense category and currency lookup: Ask the agent to fetch available expense categories or supported currencies, helping you record transactions accurately and consistently.
  • Account and profile insights: Let your agent pull your current user details so you can quickly review account information or verify profile data as needed.

What is the Composio tool router, and how does it fit here?

What is Composio SDK?

Composio's Composio SDK helps agents find the right tools for a task at runtime. You can plug in multiple toolkits (like Gmail, HubSpot, and GitHub), and the agent will identify the relevant app and action to complete multi-step workflows. This can reduce token usage and improve the reliability of tool calls. Read more here: Getting started with Composio SDK

The tool router generates a secure MCP URL that your agents can access to perform actions.

How the Composio SDK works

The Composio SDK follows a three-phase workflow:

  1. Discovery: Searches for tools matching your task and returns relevant toolkits with their details.
  2. Authentication: Checks for active connections. If missing, creates an auth config and returns a connection URL via Auth Link.
  3. Execution: Executes the action using the authenticated connection.

Step-by-step Guide

Step by step09 STEPS
1

Prerequisites

Before starting, make sure you have:
  • Node.js 18 or higher
  • A Composio account with an active API key
  • An OpenAI API key
  • Basic familiarity with TypeScript
2

Getting API Keys for OpenAI and Composio

OpenAI API Key
  • Go to the OpenAI dashboard and create an API key.
  • You need credits or a connected billing setup to use the models.
  • Store the key somewhere safe.
Composio API Key
  • Log in to the Composio dashboard.
  • Go to Settings and copy your API key.
  • This key lets your Mastra agent talk to Composio and reach Splitwise through MCP.
3

Install dependencies

bash
npm install @composio/core @mastra/core @mastra/mcp @ai-sdk/openai dotenv

Install the required packages.

What's happening:

  • @composio/core is the Composio SDK for creating MCP sessions
  • @mastra/core provides the Agent class
  • @mastra/mcp is Mastra's MCP client
  • @ai-sdk/openai is the model wrapper for OpenAI
  • dotenv loads environment variables from .env
4

Set up environment variables

bash
COMPOSIO_API_KEY=your_composio_api_key_here
COMPOSIO_USER_ID=your_user_id_here
OPENAI_API_KEY=your_openai_api_key_here

Create a .env file in your project root.

What's happening:

  • COMPOSIO_API_KEY authenticates your requests to Composio
  • COMPOSIO_USER_ID tells Composio which user this session belongs to
  • OPENAI_API_KEY lets the Mastra agent call OpenAI models
5

Import libraries and validate environment

typescript
import "dotenv/config";
import { openai } from "@ai-sdk/openai";
import { Agent } from "@mastra/core/agent";
import { MCPClient } from "@mastra/mcp";
import { Composio } from "@composio/core";
import * as readline from "readline";

import type { AiMessageType } from "@mastra/core/agent";

const openaiAPIKey = process.env.OPENAI_API_KEY;
const composioAPIKey = process.env.COMPOSIO_API_KEY;
const composioUserID = process.env.COMPOSIO_USER_ID;

if (!openaiAPIKey) throw new Error("OPENAI_API_KEY is not set");
if (!composioAPIKey) throw new Error("COMPOSIO_API_KEY is not set");
if (!composioUserID) throw new Error("COMPOSIO_USER_ID is not set");

const composio = new Composio({
  apiKey: composioAPIKey as string,
});
What's happening:
  • dotenv/config auto loads your .env so process.env.* is available
  • openai gives you a Mastra compatible model wrapper
  • Agent is the Mastra agent that will call tools and produce answers
  • MCPClient connects Mastra to your Composio MCP server
  • Composio is used to create a Tool Router session
6

Create a Tool Router session for Splitwise

typescript
async function main() {
  const session = await composio.create(
    composioUserID as string,
    {
      toolkits: ["splitwise"],
    },
  );

  const composioMCPUrl = session.mcp.url;
  console.log("Splitwise MCP URL:", composioMCPUrl);
What's happening:
  • create spins up a short-lived MCP HTTP endpoint for this user
  • The toolkits array contains "splitwise" for Splitwise access
  • session.mcp.url is the MCP URL that Mastra's MCPClient will connect to
7

Configure Mastra MCP client and fetch tools

typescript
const mcpClient = new MCPClient({
    id: composioUserID as string,
    servers: {
      nasdaq: {
        url: new URL(composioMCPUrl),
        requestInit: {
          headers: session.mcp.headers,
        },
      },
    },
    timeout: 30_000,
  });

console.log("Fetching MCP tools from Composio...");
const composioTools = await mcpClient.getTools();
console.log("Number of tools:", Object.keys(composioTools).length);
What's happening:
  • MCPClient takes an id for this client and a list of MCP servers
  • The headers property includes the x-api-key for authentication
  • getTools fetches the tool definitions exposed by the Splitwise toolkit
8

Create the Mastra agent

typescript
const agent = new Agent({
    name: "splitwise-mastra-agent",
    instructions: "You are an AI agent with Splitwise tools via Composio.",
    model: "openai/gpt-5",
  });
What's happening:
  • Agent is the core Mastra agent
  • name is just an identifier for logging and debugging
  • instructions guide the agent to use tools instead of only answering in natural language
  • model uses openai("gpt-5") to configure the underlying LLM
9

Set up interactive chat interface

typescript
let messages: AiMessageType[] = [];

console.log("Chat started! Type 'exit' or 'quit' to end.\n");

const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout,
  prompt: "> ",
});

rl.prompt();

rl.on("line", async (userInput: string) => {
  const trimmedInput = userInput.trim();

  if (["exit", "quit", "bye"].includes(trimmedInput.toLowerCase())) {
    console.log("\nGoodbye!");
    rl.close();
    process.exit(0);
  }

  if (!trimmedInput) {
    rl.prompt();
    return;
  }

  messages.push({
    id: crypto.randomUUID(),
    role: "user",
    content: trimmedInput,
  });

  console.log("\nAgent is thinking...\n");

  try {
    const response = await agent.generate(messages, {
      toolsets: {
        splitwise: composioTools,
      },
      maxSteps: 8,
    });

    const { text } = response;

    if (text && text.trim().length > 0) {
      console.log(`Agent: ${text}\n`);
        messages.push({
          id: crypto.randomUUID(),
          role: "assistant",
          content: text,
        });
      }
    } catch (error) {
      console.error("\nError:", error);
    }

    rl.prompt();
  });

  rl.on("close", async () => {
    console.log("\nSession ended.");
    await mcpClient.disconnect();
    process.exit(0);
  });
}

main().catch((err) => {
  console.error("Fatal error:", err);
  process.exit(1);
});
What's happening:
  • messages keeps the full conversation history in Mastra's expected format
  • agent.generate runs the agent with conversation history and Splitwise toolsets
  • maxSteps limits how many tool calls the agent can take in a single run
  • onStepFinish is a hook that prints intermediate steps for debugging

Complete Code

Here's the complete code to get you started with Splitwise and Mastra AI:

typescript
import "dotenv/config";
import { openai } from "@ai-sdk/openai";
import { Agent } from "@mastra/core/agent";
import { MCPClient } from "@mastra/mcp";
import { Composio } from "@composio/core";
import * as readline from "readline";

import type { AiMessageType } from "@mastra/core/agent";

const openaiAPIKey = process.env.OPENAI_API_KEY;
const composioAPIKey = process.env.COMPOSIO_API_KEY;
const composioUserID = process.env.COMPOSIO_USER_ID;

if (!openaiAPIKey) throw new Error("OPENAI_API_KEY is not set");
if (!composioAPIKey) throw new Error("COMPOSIO_API_KEY is not set");
if (!composioUserID) throw new Error("COMPOSIO_USER_ID is not set");

const composio = new Composio({ apiKey: composioAPIKey as string });

async function main() {
  const session = await composio.create(composioUserID as string, {
    toolkits: ["splitwise"],
  });

  const composioMCPUrl = session.mcp.url;

  const mcpClient = new MCPClient({
    id: composioUserID as string,
    servers: {
      splitwise: {
        url: new URL(composioMCPUrl),
        requestInit: {
          headers: session.mcp.headers,
        },
      },
    },
    timeout: 30_000,
  });

  const composioTools = await mcpClient.getTools();

  const agent = new Agent({
    name: "splitwise-mastra-agent",
    instructions: "You are an AI agent with Splitwise tools via Composio.",
    model: "openai/gpt-5",
  });

  let messages: AiMessageType[] = [];

  const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
    prompt: "> ",
  });

  rl.prompt();

  rl.on("line", async (input: string) => {
    const trimmed = input.trim();
    if (["exit", "quit"].includes(trimmed.toLowerCase())) {
      rl.close();
      return;
    }

    messages.push({ id: crypto.randomUUID(), role: "user", content: trimmed });

    const { text } = await agent.generate(messages, {
      toolsets: { splitwise: composioTools },
      maxSteps: 8,
    });

    if (text) {
      console.log(`Agent: ${text}\n`);
      messages.push({ id: crypto.randomUUID(), role: "assistant", content: text });
    }

    rl.prompt();
  });

  rl.on("close", async () => {
    await mcpClient.disconnect();
    process.exit(0);
  });
}

main();

Conclusion

You've built a Mastra AI agent that can interact with Splitwise through Composio's Tool Router. You can extend this further by:
  • Adding other toolkits like Gmail, Slack, or GitHub
  • Building a web-based chat interface around this agent
  • Using multiple MCP endpoints to enable cross-app workflows
TOOLS

Supported Tools

Every Splitwise action and event your agent gets out of the box.

Add Friend

Tool to add a new friend to Splitwise.

Add User to Group

Tool to add a user to a group.

Create Comment

Tool to create a comment on a specific expense.

Create Expense

Tool to create a new Splitwise expense.

Create Friends

Tool to add multiple friends at once to Splitwise.

Create Group

Tool to create a new group in Splitwise.

Delete Comment

Tool to delete a comment by its ID.

Delete Expense

Tool to delete an existing expense by its ID.

Delete Friend

Tool to delete an existing friend by ID.

Delete Group

Tool to delete a group and all associated records by its ID.

Get Categories

Tool to retrieve expense categories.

Get Comments

Tool to retrieve all comments associated with a specific expense.

Get Currencies

Tool to retrieve a list of supported currencies.

Get Current User

Tool to retrieve information about the current authenticated user.

Get Expense

Tool to retrieve detailed information about a specific expense by ID.

Get Expenses

Tool to list the current user's expenses from Splitwise account.

Get Friend Details

Tool to retrieve detailed information about a specific friend.

Get Friends

Tool to list current user's friends on Splitwise.

Get Group Details

Tool to retrieve detailed information about a specific group.

Get Groups

Retrieves all groups the authenticated user belongs to, including group details, members, balances, and debt information.

Get Notifications

Tool to retrieve recent activity notifications from the user's Splitwise account.

Get User Information

Retrieves basic profile information about any Splitwise user by their ID.

Remove User from Group

Tool to remove a user from a group.

Restore Deleted Expense

Tool to restore a previously deleted expense and its associated records.

Restore Deleted Group

Tool to restore a previously deleted group and all its associated records.

Update Expense

Tool to update an existing Splitwise expense.

Update User

Tool to update user account details including name, email, password, and preferences.

FRAMEWORKS

How to build Splitwise MCP Agent with another framework

OpenAI Agents SDK logo

OpenAI Agents SDK

Use Splitwise MCP with OpenAI Agents SDK

Claude Agent SDK logo

Claude Agent SDK

Use Splitwise MCP with Claude Agent SDK

Claude Code logo

Claude Code

Use Splitwise MCP with Claude Code

Claude Cowork logo

Claude Cowork

Use Splitwise MCP with Claude Cowork

Codex logo

Codex

Use Splitwise MCP with Codex

OpenClaw logo

OpenClaw

Use Splitwise MCP with OpenClaw

Hermes logo

Hermes

Use Splitwise MCP with Hermes

CLI logo

CLI

Use Splitwise MCP with CLI

Google ADK logo

Google ADK

Use Splitwise MCP with Google ADK

LangChain logo

LangChain

Use Splitwise MCP with LangChain

Vercel AI SDK logo

Vercel AI SDK

Use Splitwise MCP with Vercel AI SDK

LlamaIndex logo

LlamaIndex

Use Splitwise MCP with LlamaIndex

CrewAI logo

CrewAI

Use Splitwise MCP with CrewAI

FAQ

Frequently asked questions

With a standalone Splitwise MCP server, the agents and LLMs can only access a fixed set of Splitwise tools tied to that server. However, with the Composio Tool Router, agents can dynamically load tools from Splitwise and many other apps based on the task at hand, all through a single MCP endpoint.

Yes, you can. Mastra AI fully supports MCP integration. You get structured tool calling, message history handling, and model orchestration while Tool Router takes care of discovering and serving the right Splitwise tools.

Yes, absolutely. You can configure which Splitwise scopes and actions are allowed when connecting your account to Composio. You can also bring your own OAuth credentials or API configuration so you keep full control over what the agent can do.

All sensitive data such as tokens, keys, and configuration is fully encrypted at rest and in transit. Composio is SOC 2 Type 2 compliant and follows strict security practices so your Splitwise data and credentials are handled as safely as possible.

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