API (Application Programming Interface)

A way for two or more computer programs to communicate with each other. Often used to integrate AI models into applications.

How it works

An API defines a contract: a set of endpoints, request formats, and response schemas that a service exposes. When you call an AI model API, you send an HTTPS request with your prompt and parameters (like temperature and max tokens), and the server returns a JSON response containing the generated text. Authentication is handled via API keys, and rate limits control usage. SDKs in Python, JavaScript, and other languages wrap these raw HTTP calls into convenient functions.

Why it matters

APIs are the primary way AI capabilities reach products. Without them, every developer would need to run expensive GPU infrastructure in-house. APIs democratise access to frontier models, letting a solo developer build a sophisticated AI-powered app in hours. They also abstract away model versioning — when a provider improves a model, applications that call the API benefit without any code changes.