What Makes a Good API?

APIs have become ubiquitous in modern technology - and in modern tech marketing. If you’ve ever looked into buying a software service or platform in the last ten years, the odds are that a good API was listed as one of the selling points. But what exactly makes an API “good?”

Before we dive into that question, let’s take a minute to recap what APIs are, and why they’ve become so central to business and technology.

API 101: What is an API?

Application Programming Interfaces (APIs) are the mechanisms that allow computer software to communicate with each other. APIs ensure that when one software system makes a request, another system can understand the request and respond correctly. When discussing the relationship between two software systems, the application sending the request for action is called the client, and the application sending the response is called the server. 

For example, your bank’s software system houses all of your banking data–that software system is the server. The banking app on your phone is the client. When you initiate actions in your banking app, like making transactions, checking your account balance, or even chatting with a representative, the app communicates with the bank’s software via its API and tells it which action to perform. The server provides an API for the client to use to perform actions.

How does an API work?

Let’s say that you want to make a transfer of funds from your checking account to your savings account. You open your banking app and navigate to the transfer tab where you are asked which account you are transferring from, which account you are transferring to, the amount you want to transfer, and any additional notes before you can submit the request. Within seconds of submitting your request, the number on your checking account decreases and the number on your savings account increases, and the physical amount of money you can withdraw from the bank for both accounts has changed.