Written by Martin Ågren - February 20, 2026
API stands for:
Application Programming Interface
A way of connecting applications. A way for different software systems to exchange data.
You might want to connect a system to an AI model, using API calls.
Or you might want to connect an AI model or AI tool to an application, using API. A newer method for this is MCP though.
Use an API key (a string of characters) to connect.
Protect your API keys against unwanted exploitation (someone else uses the key, and you pay for the API calls).
Never embed the API key in a way that others may see that string of characters.
Example:
You use the IDE Visual Studio Code (V S Code) or Cursor to write code.
You use Claude CODE via the CLI (command line interface) using your Claude subscription for the AI usage, so you don't need to pay for API calls.
But you hit your monthly limit, so you use API to pay for some extra API calls to keep using Claude AI model inside your IDE, until your monthly limit is renewed and you can continue using your Claude subscription for AI model use inside your IDE.