> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://developers.upwardli.com/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://developers.upwardli.com/_mcp/server.

# Core Concepts

> Learn about the key concepts of the Upward API.

Upward provides a secure and scalable platform that is easy to integrate into your fintech product. Through our API, you are able to access the full functionality of the Upward system to begin converting your standard purchasing and payment processes into credit-building activity for your consumers.

## URLs

| Environment               | URL                                                                                          |
| ------------------------- | -------------------------------------------------------------------------------------------- |
| Sandbox Authentication    | [https://auth-sandbox.upwardli.com/auth/token](https://auth-sandbox.upwardli.com/auth/token) |
| Sandbox API Root          | [https://api-sandbox.upwardli.com/v2](https://api-sandbox.upwardli.com/v2)                   |
| Production Authentication | [https://auth.upwardli.com/auth/token](https://auth.upwardli.com/auth/token)                 |
| Production API Root       | [https://api.upwardli.com/v2](https://api.upwardli.com/v2)                                   |

## Status Codes

The Upward API uses standard HTTP response codes to communicate the result of a request. In general, the codes indicate:

* **1xx informational response** – the request was received, continuing process
* **2xx successful** – the request was successfully received, understood, and accepted
* **3xx redirection** – further action needs to be taken in order to complete the request
* **4xx client error** – the request contains bad syntax or cannot be fulfilled
* **5xx server error** – the server failed to fulfill an apparently valid request

### HTTP Code Descriptions

| HTTP Code | Description                                                                                |
| --------- | ------------------------------------------------------------------------------------------ |
| 200       | Success                                                                                    |
| 400       | There is something wrong with the data in your request, or the request cannot be processed |
| 401       | There is an issue with your API access token                                               |
| 403       | Your API access token is good, but you don’t have permission to do what is being requested |
| 404       | The resource specified does not exist                                                      |
| 500       | We are experiencing technical difficulties                                                 |