Square with Pydantic AI

How to integrate Square MCP with Pydantic AI

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Introduction Also integrate Square with TL;DR What is Pydantic AI What is the Square MCP server Supported Tools & Triggers Creating MCP Server - Stand-alone vs Composio SDK Step-by-step Guide Complete Code Conclusion How to build Square MCP Agent with another framework Explore Other Toolkits FAQ

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Introduction

This guide walks you through connecting Square to Pydantic 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 Pydantic 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

OpenAI Agents SDK Claude Agent SDK Claude Code Claude Cowork Codex OpenClaw Hermes CLI Google ADK LangChain Vercel AI SDK Mastra AI LlamaIndex CrewAI

TL;DR

Here's what you'll learn:

How to set up your Composio API key and User ID
How to create a Composio Tool Router session for Square
How to attach an MCP Server to a Pydantic AI agent
How to stream responses and maintain chat history
How to build a simple REPL-style chat interface to test your Square workflows

What is Pydantic AI?

Pydantic AI is a Python framework for building AI agents with strong typing and validation. It leverages Pydantic's data validation capabilities to create robust, type-safe AI applications.

Key features include:

Type Safety: Built on Pydantic for automatic data validation
MCP Support: Native support for Model Context Protocol servers
Streaming: Built-in support for streaming responses
Async First: Designed for async/await patterns

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:

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

Step-by-step Guide

Prerequisites

Before starting, make sure you have:

Python 3.9 or higher
A Composio account with an active API key
Basic familiarity with Python and async programming

Getting API Keys for OpenAI and Composio

OpenAI API Key

Go to the OpenAI dashboard and create an API key. You'll need credits to use the models, or you can connect to another model provider.
Keep the API key safe.

Composio API Key

Log in to the Composio dashboard.
Navigate to your API settings and generate a new API key.
Store this key securely as you'll need it for authentication.

Install dependencies

bash

pip install composio pydantic-ai python-dotenv

Install the required libraries.

What's happening:

composio connects your agent to external SaaS tools like Square
pydantic-ai lets you create structured AI agents with tool support
python-dotenv loads your environment variables securely from a .env file

Set up environment variables

bash

COMPOSIO_API_KEY=your_composio_api_key_here
USER_ID=your_user_id_here
OPENAI_API_KEY=your_openai_api_key

Create a .env file in your project root.

What's happening:

COMPOSIO_API_KEY authenticates your agent to Composio's API
USER_ID associates your session with your account for secure tool access
OPENAI_API_KEY to access OpenAI LLMs

Import dependencies

python

import asyncio
import os
from dotenv import load_dotenv
from composio import Composio
from pydantic_ai import Agent
from pydantic_ai.mcp import MCPServerStreamableHTTP

load_dotenv()

What's happening:

We load environment variables and import required modules
Composio manages connections to Square
MCPServerStreamableHTTP connects to the Square MCP server endpoint
Agent from Pydantic AI lets you define and run the AI assistant

Create a Tool Router Session

python

async def main():
    api_key = os.getenv("COMPOSIO_API_KEY")
    user_id = os.getenv("USER_ID")
    if not api_key or not user_id:
        raise RuntimeError("Set COMPOSIO_API_KEY and USER_ID in your environment")

    # Create a Composio Tool Router session for Square
    composio = Composio(api_key=api_key)
    session = composio.create(
        user_id=user_id,
        toolkits=["square"],
    )
    url = session.mcp.url
    if not url:
        raise ValueError("Composio session did not return an MCP URL")

What's happening:

We're creating a Tool Router session that gives your agent access to Square tools
The create method takes the user ID and specifies which toolkits should be available
The returned session.mcp.url is the MCP server URL that your agent will use

Initialize the Pydantic AI Agent

python

# Attach the MCP server to a Pydantic AI Agent
square_mcp = MCPServerStreamableHTTP(url, headers={"x-api-key": COMPOSIO_API_KEY})
agent = Agent(
    "openai:gpt-5",
    toolsets=[square_mcp],
    instructions=(
        "You are a Square assistant. Use Square tools to help users "
        "with their requests. Ask clarifying questions when needed."
    ),
)

What's happening:

The MCP client connects to the Square endpoint
The agent uses GPT-5 to interpret user commands and perform Square operations
The instructions field defines the agent's role and behavior

Build the chat interface

python

# Simple REPL with message history
history = []
print("Chat started! Type 'exit' or 'quit' to end.\n")
print("Try asking the agent to help you with Square.\n")

while True:
    user_input = input("You: ").strip()
    if user_input.lower() in {"exit", "quit", "bye"}:
        print("\nGoodbye!")
        break
    if not user_input:
        continue

    print("\nAgent is thinking...\n", flush=True)

    async with agent.run_stream(user_input, message_history=history) as stream_result:
        collected_text = ""
        async for chunk in stream_result.stream_output():
            text_piece = None
            if isinstance(chunk, str):
                text_piece = chunk
            elif hasattr(chunk, "delta") and isinstance(chunk.delta, str):
                text_piece = chunk.delta
            elif hasattr(chunk, "text"):
                text_piece = chunk.text
            if text_piece:
                collected_text += text_piece
        result = stream_result

    print(f"Agent: {collected_text}\n")
    history = result.all_messages()

What's happening:

The agent reads input from the terminal and streams its response
Square API calls happen automatically under the hood
The model keeps conversation history to maintain context across turns

Run the application

python

if __name__ == "__main__":
    asyncio.run(main())

What's happening:

The asyncio loop launches the agent and keeps it running until you exit

Complete Code

Here's the complete code to get you started with Square and Pydantic AI:

python

import asyncio
import os
from dotenv import load_dotenv
from composio import Composio
from pydantic_ai import Agent
from pydantic_ai.mcp import MCPServerStreamableHTTP

load_dotenv()

async def main():
    api_key = os.getenv("COMPOSIO_API_KEY")
    user_id = os.getenv("USER_ID")
    if not api_key or not user_id:
        raise RuntimeError("Set COMPOSIO_API_KEY and USER_ID in your environment")

    # Create a Composio Tool Router session for Square
    composio = Composio(api_key=api_key)
    session = composio.create(
        user_id=user_id,
        toolkits=["square"],
    )
    url = session.mcp.url
    if not url:
        raise ValueError("Composio session did not return an MCP URL")

    # Attach the MCP server to a Pydantic AI Agent
    square_mcp = MCPServerStreamableHTTP(url, headers={"x-api-key": COMPOSIO_API_KEY})
    agent = Agent(
        "openai:gpt-5",
        toolsets=[square_mcp],
        instructions=(
            "You are a Square assistant. Use Square tools to help users "
            "with their requests. Ask clarifying questions when needed."
        ),
    )

    # Simple REPL with message history
    history = []
    print("Chat started! Type 'exit' or 'quit' to end.\n")
    print("Try asking the agent to help you with Square.\n")

    while True:
        user_input = input("You: ").strip()
        if user_input.lower() in {"exit", "quit", "bye"}:
            print("\nGoodbye!")
            break
        if not user_input:
            continue

        print("\nAgent is thinking...\n", flush=True)

        async with agent.run_stream(user_input, message_history=history) as stream_result:
            collected_text = ""
            async for chunk in stream_result.stream_output():
                text_piece = None
                if isinstance(chunk, str):
                    text_piece = chunk
                elif hasattr(chunk, "delta") and isinstance(chunk.delta, str):
                    text_piece = chunk.delta
                elif hasattr(chunk, "text"):
                    text_piece = chunk.text
                if text_piece:
                    collected_text += text_piece
            result = stream_result

        print(f"Agent: {collected_text}\n")
        history = result.all_messages()

if __name__ == "__main__":
    asyncio.run(main())

Conclusion

You've built a Pydantic AI agent that can interact with Square through Composio's Tool Router. With this setup, your agent can perform real Square actions through natural language. You can extend this further by:

Adding other toolkits like Gmail, HubSpot, or Salesforce
Building a web-based chat interface around this agent
Using multiple MCP endpoints to enable cross-app workflows (for example, Gmail + Square for workflow automation)

This architecture makes your AI agent "agent-native", able to securely use APIs in a unified, composable way without custom integrations.

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CLI

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TOOLKIT MARKETPLACE

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 Pydantic AI?

Yes, you can. Pydantic 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.

Used by agents from

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We handle tool reliability, observability, and security so you never have to second-guess an agent action.

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Harsha GaddipatiCo-founder, Slashy

Karan skipped his own birthday party to fix our critical issue. It was 10 pm and he diverted his Waymo to help us instead. This really sets the bar, shows you the commitment you need to have when users rely on your software.

Abhi AryaCo-founder, Opennote

A lot of students tell us that the moment their connected tools start talking to each other inside Opennote feels almost magical. The agent just knows them, and it has immensely helped in keeping new users on the platform.

Nirman DaveCEO, Zams

We chose Composio over Pipedream because it delivered depth where it mattered. It supported niche tools and tricky edge cases that other platforms simply ignored. Giving us confidence to scale without compromising.

Ryan YuFounder, Extra Thursday

As a solo builder, shipping fast is life or death. The only way I can outcompete incumbents is by outmanoeuvring them. Getting bogged down in the complexities of managing agent auth would have been a death sentence for Extra Thursday.

Tomisin JenrolaFounder & CEO, SwarmZero

Before partnering with Composio, adding tool integrations was a slow, resource-intensive process. Each integration could take weeks or months of engineering time, and maintaining them meant constantly keeping up with API changes.

Jerome LeclancheCo-Founder, Ingram Technologies

With hands-on help from their founder, we integrated Gmail and Google Drive in just 30 minutes. This level of personal support and commitment is exactly what startups should strive for.

Harsha GaddipatiCo-founder, Slashy

Abhi AryaCo-founder, Opennote

Nirman DaveCEO, Zams

Ryan YuFounder, Extra Thursday

Tomisin JenrolaFounder & CEO, SwarmZero

Jerome LeclancheCo-Founder, Ingram Technologies

With hands-on help from their founder, we integrated Gmail and Google Drive in just 30 minutes. This level of personal support and commitment is exactly what startups should strive for.

Harsha GaddipatiCo-founder, Slashy

Abhi AryaCo-founder, Opennote

Nirman DaveCEO, Zams

Ryan YuFounder, Extra Thursday

Tomisin JenrolaFounder & CEO, SwarmZero

Jerome LeclancheCo-Founder, Ingram Technologies

With hands-on help from their founder, we integrated Gmail and Google Drive in just 30 minutes. This level of personal support and commitment is exactly what startups should strive for.

How to integrate Square MCP with Pydantic AI

Table of Contents

Connect Square without Auth hassles

Introduction

Also integrate Square with

TL;DR

What is Pydantic AI?

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

Supported Tools & Triggers

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

What is Composio SDK?

How the Composio SDK works

Step-by-step Guide

Prerequisites

Getting API Keys for OpenAI and Composio

Install dependencies

Set up environment variables

Import dependencies

Create a Tool Router Session

Initialize the Pydantic AI Agent

Build the chat interface

Run the application

Complete Code

Conclusion

How to build Square MCP Agent with another framework

OpenAI Agents SDK

Claude Agent SDK

Claude Code

Claude Cowork

Codex

OpenClaw

Hermes

CLI

Google ADK

LangChain

Vercel AI SDK

Mastra AI

LlamaIndex

CrewAI

Explore Other Toolkits

Addresszen

Asin data api

Baselinker

FAQ

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

Can I use Tool Router MCP with Pydantic AI?

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

How safe is my data with Composio Tool Router?

Used by agents from

Never worry about agent reliability