GPT-4 Meets Finance: Automate Transaction Categorization with Express API

Author: Shane Larson
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Ready to sprinkle some AI stardust on your financial applications? Join us on an exhilarating journey as we explore a Node.js Express API powered by OpenAI's GPT-4 model to automate transaction categorization like never before. Embrace the future of smart budgeting, and follow our step-by-step guide that'll have you testing your innovative API with Postman in no time. Let's embark on this exciting adventure together and make financial management a walk in the park for your users!

Are you a developer looking to add a dash of AI magic to your financial applications? Look no further! In this article, we'll guide you through the process of installing and running a Node.js Express API that harnesses the incredible power of OpenAI's GPT-4 model to categorize financial transactions automatically. With a GitHub repository at your fingertips and the ability to test your shiny new API using Postman, you'll be ready to revolutionize budget categorization for your users in no time. Let's dive into this exciting adventure and make managing finances a breeze!

a van gogh style painting of an accountant budgeting at their desk


Before diving into the installation and setup process, make sure you meet the following prerequisites to ensure a smooth experience:

Basic knowledge of JavaScript and Node.js: Familiarity with JavaScript programming and Node.js will help you understand the code and make necessary modifications if required.

Node.js and npm installed: You'll need Node.js (version 12 or higher) and npm (the Node.js package manager) installed on your local machine. You can download the latest version from the official Node.js website:

Git installed: Git is required to clone the repository. If you don't have it installed, you can download it from the official website:

Postman: To test the API, you will need Postman, a popular API testing tool. Download and install it from the official website:

OpenAI API key: You'll need an OpenAI API key to access the GPT-4 model. To obtain an API key, you must sign up for an account with OpenAI:

Once you have these prerequisites in place, you're all set to begin the installation and setup process.

Step 1: Clone the Git repository

First, you'll need to clone the Git repository to your local machine. Open your terminal (or command prompt on Windows), navigate to your desired directory, and run the following command:

git clone

This command will create a new folder named gptbudgetcategorizer and copy the necessary files into it.

You can take a look at the repo on github: github repo

Step 2: Install the dependencies

Next, navigate to the newly created directory:

cd gpt_budget_categorizer

Before you can run the application, you need to install its dependencies. Run the following command to install the necessary packages:

npm install

Step 3: Set up the environment variables

You'll need to provide an API key for OpenAI's API. Create a .env file in the root directory of the project and add the following line, replacing yourapikey with your actual OpenAI API key:


Step 4: Run the application

With the dependencies installed and environment variables set up, you can now run the application. Start the server by running:

npm start

You should see a message in the terminal indicating that the server is listening on port 3000 (or another port, if you've configured it differently).

Step 5: Test the API with Postman

Now that the server is running, you can use Postman to test the API. Create a new POST request with the following URL:


Postman Request for GPT-4 Budget Categorizer

In the "Body" tab, select "raw" and set the content type to "JSON." Then, paste the following JSON data into the request body, adjusting the categories and memo as needed:

  "categories": ["groceries", "utilities", "entertainment", "transportation"],
  "memo": "Transaction: 12345, Description: Electricity bill payment"

Send the request, and you should receive a JSON response containing the generated budget category for the transaction:

  "category": "utilities"


In this article, we have shown you how to install and run a Node.js Express API that uses GPT-4 to automatically categorize financial transactions. You can now use this API to process and categorize transactions in your applications, making your budget management tasks more efficient and accurate.

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