Glossary term

API

Application programming interface: a way for software to request services, such as a model's output, from another system.

How it works

An API is a defined way for one program to ask another for something. Most AI models are offered through a web API: you send a request, such as a prompt, and get a response back, usually as JSON. Providers charge by usage, often per token.

Calling a model API

Step 1Your app sends a request
Step 2Provider runs the model
Step 3Response returns as JSON
Step 4Your app uses it

In code

A typical API request

import requests

response = requests.post(
    "https://api.example.com/v1/chat",
    headers={"Authorization": "Bearer YOUR_KEY"},
    json={"model": "model-name", "messages": [{"role": "user", "content": "Hello"}]},
)
print(response.json())

Why it matters

APIs let developers build products on top of models without running any AI hardware.

Related terms

SDK Model serving Function calling