How to integrate Square MCP with Mastra AI

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Introduction

This guide walks you through connecting Square to Mastra AI using the Composio tool router. By the end, you'll have a working Square agent that can create and send an invoice to a customer, list all recent payments from last week, update item prices in your product catalog through natural language commands.

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

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

Also integrate Square with

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 Square tools
  • Connect Mastra's MCP client to the Composio generated MCP URL
  • Fetch Square 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 Square 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 Square MCP server, and what's possible with it?

The Square MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to your Square account. It provides structured and secure access to your Square business tools, so your agent can perform actions like processing payments, managing invoices, tracking orders, handling customers, and managing inventory on your behalf.

  • Seamless payment processing: Let your agent accept card payments, issue refunds, and manage transactions across your business locations.
  • Automated invoice creation and management: Ask your agent to generate, send, and monitor invoices for your customers, streamlining your billing process.
  • Order and fulfillment tracking: Enable your agent to view, update, and manage orders, helping you keep tabs on fulfillment and delivery status with ease.
  • Customer profile management: Have your agent create, update, or search customer profiles, making it easier to personalize service and maintain up-to-date records.
  • Inventory and item catalog control: Allow your agent to track stock levels, update item details, and organize your catalog for smooth retail operations.

Supported Tools & Triggers

Tools
Accept DisputeAccept a dispute and acknowledge liability, returning funds to the cardholder.
Add Group to CustomerTool to add a customer to a customer group.
Calculate OrderTool to preview order pricing without creating an order.
Cancel InvoiceCancels a Square invoice, preventing further payments from being collected.
Cancel PaymentCancels (voids) a payment that is in APPROVED status.
Create Bulk CustomersTool to create multiple customer profiles in a single request.
Create CardTool to create a card on file.
Create CustomerTool to create a new customer profile in Square.
Create Customer Custom Attribute DefinitionTool to create a customer-related custom attribute definition.
Create Customer GroupTool to create a new customer group for a business.
Create Dispute Evidence FileTool to upload a file as dispute evidence.
Create Dispute Evidence TextUpload text evidence for a dispute challenge.
Create Invoice AttachmentUpload and attach a file to a Square invoice.
Create LocationTool to create a new business location in a Square account.
Create Location Custom Attribute DefinitionTool to create a location-related custom attribute definition.
Delete CustomerTool to delete a Square customer profile.
Delete Customer Custom AttributeTool to delete a custom attribute from a customer profile.
Delete Customer Custom Attribute DefinitionTool to delete a customer-related custom attribute definition.
Delete Customer GroupTool to delete a customer group by its ID.
Bulk Delete CustomersTool to bulk delete customer profiles from Square.
Delete Dispute EvidenceRemoves a specific piece of evidence from a dispute.
Delete InvoiceTool to delete a Square invoice (only DRAFT invoices can be deleted).
Delete Invoice AttachmentTool to delete an attachment from a Square invoice.
Delete Location Custom AttributeTool to delete a custom attribute from a location.
Delete Location Custom Attribute DefinitionTool to delete a location-related custom attribute definition.
Delete Locations Custom Attributes (Batch)Tool to delete custom attributes from multiple locations in a single batch request.
Delete Merchant Custom AttributeTool to delete a custom attribute from a merchant profile.
Delete Merchant Custom Attribute DefinitionTool to delete a merchant-related custom attribute definition.
Delete Merchants Custom Attributes (Batch)Tool to delete custom attributes from multiple merchants in a single batch request.
Delete Webhook SubscriptionPermanently deletes a webhook subscription by its ID.
Get Business Booking ProfileTool to retrieve the business booking profile for a Square merchant via GraphQL.
Get Current MerchantTool to retrieve merchant information associated with the access token using Square's GraphQL API.
Get Customer Custom AttributeRetrieves a custom attribute from a customer profile in Square.
Get Customer Custom Attribute DefinitionTool to retrieve a customer-related custom attribute definition from Square.
Get Customers via GraphQLTool to retrieve customer profiles from Square Customer Directory using GraphQL API.
Get Dispute EvidenceRetrieves detailed information about a specific piece of evidence that was uploaded for a dispute.
Get InvoiceRetrieves detailed information about a specific Square invoice by its ID.
Get MerchantTool to retrieve detailed information about a specific Square merchant by ID.
Get Online Checkout Location SettingsTool to retrieve location-level settings for Square online checkout.
List ChannelsTool to list requested channels from Square.
List Customer Custom Attribute DefinitionsTool to list customer-related custom attribute definitions from Square.
List Customer Custom Attribute Definitions (GraphQL)Tool to retrieve customer custom attribute definitions via Square's GraphQL API.
List Customer Custom AttributesTool to list custom attributes for a customer profile.
List Customer GroupsTool to retrieve the list of customer groups of a business.
List CustomersTool to retrieve customer profiles associated with a Square account.
List Customer SegmentsTool to retrieve the list of customer segments of a business.
List Dispute EvidenceTool to list evidence items associated with a given dispute.
List InvoicesTool to list invoices for a Square location.
List Location Custom Attribute DefinitionsTool to list location-related custom attribute definitions from Square.
List LocationsTool to retrieve all business locations from a Square account.
List Locations Custom AttributesTool to list custom attributes for a specific location in Square.
List Merchant Custom Attribute DefinitionsTool to list merchant-related custom attribute definitions from Square.
List MerchantsTool to retrieve merchant account information associated with the access token.
List Merchants Custom AttributesTool to list custom attributes for a specific merchant in Square.
List PaymentsTool to list payments by location and time range to enable reconciliation and net sales reporting from Square POS.
List Webhook Event TypesTool to list available webhook event types.
List Webhook SubscriptionsList all webhook subscriptions owned by your application.
Remove Group From CustomerRemoves a customer from a customer group.
Retrieve Bulk CustomersTool to retrieve multiple customer profiles in a single request.
Retrieve ChannelRetrieve a Square channel by its ID.
Bulk Retrieve ChannelsTool to bulk retrieve multiple Square channels by their IDs in a single request.
Retrieve CustomerTool to retrieve detailed information about a specific Square customer by ID.
Retrieve Customer GroupTool to retrieve a specific Square customer group by ID.
Retrieve Customer SegmentTool to retrieve a specific customer segment by its ID.
Retrieve DisputeTool to retrieve a Square dispute by ID.
Retrieve LocationTool to retrieve detailed information about a specific Square location by ID.
Retrieve Location Custom AttributeRetrieves a custom attribute associated with a location in Square.
Retrieve Location Custom Attribute DefinitionTool to retrieve a location-related custom attribute definition.
Retrieve Merchant Custom AttributeRetrieves a custom attribute associated with a merchant in Square.
Retrieve Merchant Custom Attribute DefinitionTool to retrieve a merchant-related custom attribute definition from Square.
Retrieve MerchantsTool to retrieve merchant information including status, main location details, and capabilities using Square's GraphQL API.
Retrieve OrderRetrieves detailed information about a specific Square order by its ID.
Retrieve Payment LinkRetrieves a Square-hosted payment link by ID.
Retrieve Token StatusTool to retrieve information about an OAuth access token or personal access token.
Retrieve Webhook SubscriptionRetrieve a Square webhook subscription by its ID.
Search CustomersTool to search customer profiles in Square Customer Directory.
Search OrdersTool to search orders across one or more Square locations with filters.
Submit Dispute EvidenceSubmits evidence for a dispute to the cardholder's bank.
Test Webhook SubscriptionTests a webhook subscription by sending a test event to the configured notification URL.
Update CustomerTool to update an existing Square customer profile.
Update Customer Custom Attribute DefinitionTool to update a customer-related custom attribute definition in Square.
Update Customer GroupTool to update a customer group's information by its ID.
Bulk Update CustomersTool to update multiple customer profiles in a single batch operation.
Update LocationTool to update an existing business location in a Square account.
Update Location Custom Attribute DefinitionTool to update a location-related custom attribute definition in Square.
Update Merchant Custom Attribute DefinitionTool to update a merchant-related custom attribute definition in Square.
Update Online Checkout Location SettingsTool to update location-level settings for Square online checkout.
Update OrderUpdates an existing Square order by adding, modifying, or removing fields.
Update Webhook SubscriptionTool to update a Square webhook subscription.
Update Webhook Subscription Signature KeyTool to rotate the signature key for a webhook subscription.
Upsert Customer Custom AttributeTool to create or update a custom attribute for a customer profile.
Batch Upsert Customer Custom AttributesTool to create or update custom attributes for multiple customers in a single batch request.
Upsert Location Custom AttributeTool to create or update a custom attribute for a location.
Batch Upsert Locations Custom AttributesTool to create or update custom attributes for multiple locations in a single batch request.
Upsert Merchant Custom AttributeTool to create or update a custom attribute for a merchant profile.
Batch Upsert Merchants Custom AttributesTool to create or update custom attributes for multiple merchants in a single batch request.

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

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

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 Square through MCP.

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

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

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

Create a Tool Router session for Square

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

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

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 Square toolkit

Create the Mastra agent

typescript
const agent = new Agent({
    name: "square-mastra-agent",
    instructions: "You are an AI agent with Square 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

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: {
        square: 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 Square 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 Square 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: ["square"],
  });

  const composioMCPUrl = session.mcp.url;

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

  const composioTools = await mcpClient.getTools();

  const agent = new Agent({
    name: "square-mastra-agent",
    instructions: "You are an AI agent with Square 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: { square: 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 Square 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

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FAQ

What are the differences in Tool Router MCP and Square MCP?

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

Can I use Tool Router MCP with Mastra AI?

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 Square tools.

Can I manage the permissions and scopes for Square while using Tool Router?

Yes, absolutely. You can configure which Square 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.

How safe is my data with Composio Tool Router?

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 Square data and credentials are handled as safely as possible.

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