How to integrate Taxjar MCP with Claude Code

Manage your Taxjar directly from Claude Code with zero worries about OAuth hassles, API-breaking issues, or reliability and security concerns. You can do this in two different ways: Via Composio Connect - Direct and easiest approach Via Composio SDK - Programmatic approach with more control

Taxjar logoTaxjar
Api Key

TaxJar is a trusted sales tax automation platform for ecommerce and SaaS businesses. It delivers real-time tax calculations, accurate reporting, and seamless filing across all US states.

21 Tools

Introduction

Manage your Taxjar directly from Claude Code with zero worries about OAuth hassles, API-breaking issues, or reliability and security concerns.

You can do this in two different ways:

  1. Via Composio Connect - Direct and easiest approach
  2. Via Composio SDK - Programmatic approach with more control

Also integrate Taxjar with

Why use Composio?

  • Only one MCP URL to connect multiple apps with Claude Code with zero auth hassles.
  • Programmatic tool calling allows LLMs to write its code in a remote workbench to handle complex tool chaining. Reduces to-and-fro with LLMs for frequent tool calling.
  • Handling Large tool responses out of LLM context to minimize context rot.
  • Dynamic just-in-time access to 20,000 tools across 1000+ other Apps for cross-app workflows. It loads the tools you need, so LLMs aren't overwhelmed by tools you don't need.

Connecting Taxjar to Claude Code using Composio

1. Add the Composio MCP to Claude

Terminal

2. Start Claude Code

bash
claude

3. Open your MCP list

bash
/mcp

4. Select Composio and click on Authenticate

Select Composio and click Authenticate

5. This will redirect you to the Composio OAuth page. Complete the flow by authorizing Composio and you're all set.

Composio OAuth authorization page
Composio authorization complete
Ask Claude to connect to your account and authenticate via the link

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

The Taxjar MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to your Taxjar account. It provides structured and secure access to your sales tax data, so your agent can perform actions like calculating sales tax, managing transactions, listing customers, and monitoring nexus regions on your behalf.

  • Real-time tax calculation for orders: Instantly calculate accurate sales tax for new orders, factoring in nexus addresses, line items, shipping, and exemptions.
  • Order and refund transaction management: Let your agent create, list, or delete order and refund transactions to streamline your sales and returns workflow.
  • Customer database access: Effortlessly retrieve, list, or delete customer records for tax reporting and compliance purposes.
  • Nexus region insights: Quickly identify and list all nexus regions where your business has sales tax obligations.
  • Automated transaction reporting: Access up-to-date lists of transactions and refunds for reconciliation, filing, and audit readiness.

Connecting Taxjar via Composio SDK

Composio SDK is the underlying tech that powers Rube. It's a universal gateway that does everything Rube does but with much more programmatic control. You can programmatically generate an MCP URL with the app you need (here Taxjar) for even more tool search precision. It's secure and reliable.

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 step10 STEPS
1

Prerequisites

Before starting, make sure you have:
  • Claude Pro, Max, or API billing enabled Anthropic account
  • Composio API Key
  • A Taxjar account
  • Basic knowledge of Python or TypeScript
2

Install Claude Code

bash
# macOS, Linux, WSL
curl -fsSL https://claude.ai/install.sh | bash

# Windows PowerShell
irm https://claude.ai/install.ps1 | iex

# Windows CMD
curl -fsSL https://claude.ai/install.cmd -o install.cmd && install.cmd && del install.cmd

To install Claude Code, use one of the following methods based on your operating system:

3

Set up Claude Code

bash
cd your-project-folder
claude

Open a terminal, go to your project folder, and start Claude Code:

  • Claude Code will open in your terminal
  • Follow the prompts to sign in with your Anthropic account
  • Complete the authentication flow
  • Once authenticated, you can start using Claude Code
Claude Code initial setup showing sign-in prompt
Claude Code terminal after successful login
4

Set up environment variables

bash
COMPOSIO_API_KEY=your_composio_api_key_here
USER_ID=your_user_id_here

Create a .env file in your project root with the following variables:

  • COMPOSIO_API_KEY authenticates with Composio (get it from Composio dashboard)
  • USER_ID identifies the user for session management (use any unique identifier)
5

Install Composio library

npm install @composio/core dotenv

Install the Composio TypeScript library to create MCP sessions.

  • @composio/core provides the core Composio functionality
  • dotenv loads environment variables from your .env file
6

Generate Composio MCP URL

import 'dotenv/config';
import { Composio } from '@composio/core';

const { COMPOSIO_API_KEY, USER_ID } = process.env;

if (!COMPOSIO_API_KEY || !USER_ID) {
  throw new Error('COMPOSIO_API_KEY and USER_ID required in .env');
}

const composioClient = new Composio({ apiKey: COMPOSIO_API_KEY });

const composioSession = await composioClient.create(USER_ID, {
  toolkits: ['taxjar'],
});

const composioMcpUrl = composioSession?.mcp.url;

console.log(`MCP URL: ${composioMcpUrl}`);
console.log(`\nUse this command to add to Claude Code:`);
console.log(`claude mcp add --transport http taxjar-composio "${composioMcpUrl}" --headers "X-API-Key:${COMPOSIO_API_KEY}"`);

Create a script to generate a Composio MCP URL for Taxjar. This URL will be used to connect Claude Code to Taxjar.

What's happening

  • We import the Composio client and load environment variables
  • Create a Composio instance with your API key
  • Call create() to create a Tool Router session for Taxjar
  • The returned mcp.url is the MCP server URL that Claude Code will use
  • The script prints this URL so you can copy it
7

Run the script and copy the MCP URL

node --loader ts-node/esm generate_mcp_url.ts
# or if using tsx
tsx generate_mcp_url.ts

Run your TypeScript script to generate the MCP URL.

  • The script connects to Composio and creates a Tool Router session
  • It prints the MCP URL and the exact command you need to run
  • Copy the entire claude mcp add command from the output
8

Add Taxjar MCP to Claude Code

bash
claude mcp add --transport http taxjar-composio "YOUR_MCP_URL_HERE" --headers "X-API-Key:YOUR_COMPOSIO_API_KEY"

# Then restart Claude Code
exit
claude

In your terminal, add the MCP server using the command from the previous step. The command format is:

  • claude mcp add registers a new MCP server with Claude Code
  • --transport http specifies that this is an HTTP-based MCP server
  • The server name (taxjar-composio) is how you'll reference it
  • The URL points to your Composio Tool Router session
  • --headers includes your Composio API key for authentication

After running the command, close the current Claude Code session and start a new one for the changes to take effect.

9

Verify the installation

bash
claude mcp list

Check that your Taxjar MCP server is properly configured.

  • This command lists all MCP servers registered with Claude Code
  • You should see your taxjar-composio entry in the list
  • This confirms that Claude Code can now access Taxjar tools

If everything is wired up, you should see your taxjar-composio entry listed:

Claude Code MCP list showing the toolkit MCP server
10

Authenticate Taxjar

The first time you try to use Taxjar tools, you'll be prompted to authenticate.

  • Claude Code will detect that you need to authenticate with Taxjar
  • It will show you an authentication link
  • Open the link in your browser (or copy/paste it)
  • Complete the Taxjar authorization flow
  • Return to the terminal and start using Taxjar through Claude Code

Once authenticated, you can ask Claude Code to perform Taxjar operations in natural language. For example:

  • "Calculate sales tax for a new order"
  • "List all order transactions this month"
  • "Show my current nexus regions"

Complete Code

Here's the complete code to get you started with Taxjar and Claude Code:

import 'dotenv/config';
import { Composio } from '@composio/core';

const { COMPOSIO_API_KEY, USER_ID } = process.env;

if (!COMPOSIO_API_KEY || !USER_ID) {
  throw new Error('COMPOSIO_API_KEY and USER_ID required in .env');
}

const composioClient = new Composio({ apiKey: COMPOSIO_API_KEY });

const composioSession = await composioClient.create(USER_ID, {
  toolkits: ['taxjar'],
});

const composioMcpUrl = composioSession?.mcp.url;

console.log(`MCP URL: ${composioMcpUrl}`);
console.log(`\nUse this command to add to Claude Code:`);
console.log(`claude mcp add --transport http taxjar-composio "${composioMcpUrl}" --headers "X-API-Key:${COMPOSIO_API_KEY}"`);

Conclusion

You've successfully integrated Taxjar with Claude Code using Composio's MCP server. Now you can interact with Taxjar directly from your terminal using natural language commands.

Key features of this setup:

  • Terminal-native experience without switching contexts
  • Natural language commands for Taxjar operations
  • Secure authentication through Composio's managed MCP
  • Tool Router for dynamic tool discovery and execution

Next steps:

  • Try asking Claude Code to perform various Taxjar operations
  • Add more toolkits to your Tool Router session for multi-app workflows
  • Integrate this setup into your development workflow for increased productivity

You can extend this by adding more toolkits, implementing custom workflows, or building automation scripts that leverage Claude Code's capabilities.

TOOLS

Supported Tools

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

Calculate Sales Tax For An Order

Tool to calculate sales tax for an order.

Create Customer

Tool to create a new customer with exemption information.

Create Order Transaction

Creates a new order transaction in TaxJar for sales tax reporting and compliance.

Create Refund Transaction

Tool to create a new refund transaction.

Delete Customer

Tool to delete an existing customer.

Delete Order Transaction

Tool to delete an existing order transaction.

Delete Refund Transaction

Tool to delete an existing refund transaction.

List Customers

Lists all customer IDs from your TaxJar account.

List Nexus Regions

Tool to list existing nexus regions for an account.

List Order Transactions

List order transaction IDs within a date range.

List refund transactions

Lists refund transaction IDs within a specified date range.

List Tax Categories

Tool to list all product tax categories and their codes.

Show Customer

Tool to show an existing customer.

Show Order Transaction

Tool to show an existing order transaction by ID.

Show Refund Transaction

Retrieves detailed information about a specific refund transaction from TaxJar.

Show Tax Rates for a Location

Tool to show sales tax rates for a location.

Summarize Tax Rates for All Regions

Tool to retrieve minimum and average sales tax rates by region.

Update Customer

Tool to update an existing customer in TaxJar.

Update Order Transaction

Tool to update an existing order transaction.

Update Refund Transaction

Tool to update an existing refund transaction.

Validate VAT Number

Validates EU VAT identification numbers against the VIES (VAT Information Exchange System) database.

FAQ

Frequently asked questions

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

Yes, you can. Claude Code 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 Taxjar tools.

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

Start with Taxjar.It takes 30 seconds.

Managed auth, hosted MCP servers, and every Taxjar tool your agent needs.Free to start.

Start building