How to integrate Quaderno MCP with Pydantic AI

This guide walks you through connecting Quaderno to Pydantic AI using the Composio tool router. By the end, you'll have a working Quaderno agent that can calculate tax rate for a u.s. sale, create an invoice for a new customer, email finalized invoice to a client through natural language commands. This guide will help you understand how to give your Pydantic AI agent real control over a Quaderno account through Composio's Quaderno MCP server. Before we dive in, let's take a quick look at the key ideas and tools involved.

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Api Key

Quaderno is a tax compliance platform that automates tax calculations, invoicing, and reporting for businesses globally. It helps you streamline tax processes and stay compliant without manual effort.

76 Tools

Introduction

This guide walks you through connecting Quaderno to Pydantic AI using the Composio tool router. By the end, you'll have a working Quaderno agent that can calculate tax rate for a u.s. sale, create an invoice for a new customer, email finalized invoice to a client through natural language commands.

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

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

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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 Quaderno
  • 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 Quaderno 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 Quaderno MCP server, and what's possible with it?

The Quaderno MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to your Quaderno account. It provides structured and secure access to your tax automation, invoicing, and compliance workflows, so your agent can calculate taxes, generate invoices, manage contacts and products, and handle essential document delivery on your behalf.

  • Automated tax rate calculation: Ask your agent to instantly determine the correct tax rate for any address or transaction type before creating invoices or processing sales.
  • Invoice creation and delivery: Let your agent generate detailed invoices for customers and deliver them directly via email, ensuring seamless billing operations.
  • Contact and product management: Easily create new customer or vendor contacts, add new products, or permanently delete outdated items from your Quaderno account—all through your agent.
  • Expense and tax ID cleanup: Direct your agent to remove specific expenses or registered tax IDs when they're no longer needed, keeping your records tidy and up to date.
  • Credit note and coupon handling: Your agent can deliver finalized credit notes to customers and permanently delete coupons as part of your accounting and revenue operations.

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:
  • Python 3.9 or higher
  • A Composio account with an active API key
  • Basic familiarity with Python and async programming
2

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.
3

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 Quaderno
  • pydantic-ai lets you create structured AI agents with tool support
  • python-dotenv loads your environment variables securely from a .env file
4

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
5

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 Quaderno
  • MCPServerStreamableHTTP connects to the Quaderno MCP server endpoint
  • Agent from Pydantic AI lets you define and run the AI assistant
6

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 Quaderno
    composio = Composio(api_key=api_key)
    session = composio.create(
        user_id=user_id,
        toolkits=["quaderno"],
    )
    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 Quaderno 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
7

Initialize the Pydantic AI Agent

python
# Attach the MCP server to a Pydantic AI Agent
quaderno_mcp = MCPServerStreamableHTTP(url, headers={"x-api-key": COMPOSIO_API_KEY})
agent = Agent(
    "openai:gpt-5",
    toolsets=[quaderno_mcp],
    instructions=(
        "You are a Quaderno assistant. Use Quaderno tools to help users "
        "with their requests. Ask clarifying questions when needed."
    ),
)
What's happening:
  • The MCP client connects to the Quaderno endpoint
  • The agent uses GPT-5 to interpret user commands and perform Quaderno operations
  • The instructions field defines the agent's role and behavior
8

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 Quaderno.\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
  • Quaderno API calls happen automatically under the hood
  • The model keeps conversation history to maintain context across turns
9

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 Quaderno 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 Quaderno
    composio = Composio(api_key=api_key)
    session = composio.create(
        user_id=user_id,
        toolkits=["quaderno"],
    )
    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
    quaderno_mcp = MCPServerStreamableHTTP(url, headers={"x-api-key": COMPOSIO_API_KEY})
    agent = Agent(
        "openai:gpt-5",
        toolsets=[quaderno_mcp],
        instructions=(
            "You are a Quaderno assistant. Use Quaderno 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 Quaderno.\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 Quaderno through Composio's Tool Router. With this setup, your agent can perform real Quaderno 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 + Quaderno for workflow automation)
This architecture makes your AI agent "agent-native", able to securely use APIs in a unified, composable way without custom integrations.
TOOLS

Supported Tools

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

Add Expense Payment

Adds a payment to an existing expense in Quaderno.

Calculate Tax Rate

Tool to calculate applicable tax rate for given address and transaction type.

Create Contact

Tool to create a new contact (customer or vendor).

Create Coupon

Tool to create a new discount coupon in Quaderno.

Create Estimate

Creates a new estimate/quote in Quaderno for a customer with line items.

Create Evidence

Tool to create a new location evidence for tax compliance.

Create Expense

Tool to create a business expense in Quaderno.

Create Invoice

Creates a new invoice in Quaderno for a customer with line items.

Create Product

Creates a new product that can be used as a line item in invoices, credit notes, and expenses.

Create Receipt

Creates a new receipt in Quaderno documenting payment for goods or services.

Create Recurring

Tool to create a recurring document in Quaderno that automatically generates invoices on a schedule.

Create Report Request

Tool to request a new report generation in Quaderno.

Create Tax ID

Tool to create a tax ID in a specific jurisdiction.

Create Transaction

Tool to create a sale or refund transaction in Quaderno.

Create Webhook

Tool to create a new webhook in Quaderno to receive event notifications.

Delete Contact

Tool to permanently delete a contact by ID.

Delete Coupon

Tool to permanently delete a coupon.

Delete Estimate

Permanently deletes an estimate from Quaderno by its ID.

Delete Expense

Permanently deletes an expense from Quaderno by its ID.

Delete Product

Tool to permanently delete a product by ID.

Delete Recurring

Tool to permanently delete a recurring by ID.

Delete Tax ID

Permanently deletes a registered tax ID from your Quaderno account.

Delete Webhook

Tool to permanently delete a webhook by ID.

Deliver Credit Note

Sends a credit note to the customer via email.

Deliver Estimate

Delivers an estimate to the customer via email.

Deliver Invoice

Delivers an invoice to the customer via email.

Deliver Receipt

Sends a receipt to the customer via email.

Get Authorization

Tool to retrieve account credentials and verify API access.

Get Estimate

Tool to retrieve the details of an existing estimate by ID.

List Contacts

Tool to list contacts, paginated and filterable by name, email, or tax ID.

List Coupons

Tool to list all coupons.

List Credits

Tool to list all credit notes from Quaderno.

List Estimates

Tool to list all estimates in the account, paginated and sorted by creation date (newest first).

List Evidence

Tool to list all evidence objects.

List Expenses

List all expenses from Quaderno with pagination support.

List Invoices

Tool to list all invoices from Quaderno with filtering support.

List Tax Jurisdictions

Tool to list all tax jurisdictions.

List Products

List all products (goods and services) from your Quaderno account.

List Receipts

Tool to list all receipts from Quaderno with optional filtering by search query, date range, payment state, processor ID, or customer ID.

List Recurrings

List all recurring documents (invoices, expenses, or estimates) from your Quaderno account.

List Registered Tax IDs

Tool to list all registered tax IDs.

List Reporting Requests

Retrieves all reporting requests for the account with their current status and download URLs.

List Sessions

List Quaderno Checkout sessions with optional filtering and pagination.

List Tax Codes

Tool to list all supported tax codes.

List Webhooks

Tool to list all webhooks.

Mark Invoice Uncollectible

Tool to mark an invoice as uncollectible (bad debt).

Ping API Service

Tool to check if the Quaderno API service is up and verify credentials.

Record Invoice Payment

Tool to record a payment on an existing invoice.

Remove Invoice Payment

Tool to remove a payment from an invoice.

Retrieve Contact

Tool to retrieve details of an existing contact by ID.

Retrieve Contact by Processor ID

Tool to retrieve a contact by external payment processor customer ID and gateway name.

Retrieve Coupon

Retrieve detailed information about a specific coupon by its ID.

Retrieve Credit Note

Tool to retrieve details of an existing credit note by ID.

Retrieve Evidence

Retrieves a specific evidence object by its ID.

Retrieve Expense

Tool to retrieve details of an existing expense by ID.

Retrieve Invoice

Tool to retrieve details of an existing invoice by ID.

Retrieve Tax Jurisdiction

Tool to retrieve a tax jurisdiction by ID.

Retrieve Product

Tool to retrieve details of an existing product by ID.

Retrieve Receipt

Tool to retrieve details of an existing receipt by ID.

Retrieve Recurring

Tool to retrieve details of an existing recurring document by ID.

Retrieve Reporting Request

Tool to retrieve the status and download URL of a specific report request by ID.

Retrieve Tax Code

Tool to retrieve a specific tax code by ID.

Retrieve Tax ID

Tool to retrieve details of a specific tax ID by its ID.

Update Contact

Tool to update an existing contact in Quaderno.

Update Coupon

Tool to update an existing coupon.

Update Credit Note

Tool to update a credit note.

Update Estimate

Updates an existing estimate in Quaderno by modifying allowed fields.

Update Evidence

Tool to update an evidence object.

Update Expense

Updates an existing expense in Quaderno by modifying allowed fields.

Update Invoice

Updates an existing invoice in Quaderno by modifying allowed fields.

Update product

Tool to update a product; unspecified fields remain unchanged.

Update Recurring

Tool to update a recurring document in Quaderno.

Update Tax ID

Tool to update an existing tax ID in Quaderno.

Update Webhook

Tool to update an existing webhook configuration.

Validate Tax ID

Tool to validate a tax ID.

Void Credit Note

Tool to void a credit note.

FAQ

Frequently asked questions

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

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 Quaderno tools.

Yes, absolutely. You can configure which Quaderno 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 Quaderno data and credentials are handled as safely as possible.

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