How to connect an AI API (step by step)

We’ll use the Claude (Anthropic) API as the example. The pattern is the same for OpenAI and others.

1. Go to https://console.anthropic.com and create your account.
2. In the left menu open API Keys.
3. Click Create Key, give it a name (e.g. “testing”) and copy it.

The key starts with sk-ant- and is shown only once. Save it somewhere safe; if you lose it, create another.

The key won’t work until you add a payment method and a little credit.

1. In the console open Settings → Billing.
2. Add a card and buy a small credit ($5 is plenty to practice).

It’s prepaid: you spend against that balance. You can set a monthly limit so there are no surprises.

The SDK is a library that makes talking to the API easy. Pick your language. You need PowerShellthe Terminal open.

With Python (you need Python installed):

pip install anthropic

With Node.js (you need Node.js installed):

npm install @anthropic-ai/sdk

Prefer OpenAI? It’s pip install openai or npm install openai. The rest is almost the same.

Never write the key inside your code: anyone who sees the file (or your GitHub repo) would have it. Instead, store it as an environment variable.

setx ANTHROPIC_API_KEY "sk-ant-your-key-here"

export ANTHROPIC_API_KEY="sk-ant-your-key-here"

The SDK reads that variable on its own, without you writing the key in the code.

Create a file and paste your language’s example. Change only the question text.

Python (test.py):

import anthropic

client = anthropic.Anthropic()  # reads ANTHROPIC_API_KEY from the environment

message = client.messages.create(
    model="claude-haiku-4-5",
    max_tokens=300,
    messages=[
        {"role": "user", "content": "Explain in one sentence what an API is."}
    ],
)

print(message.content[0].text)

Run:

python test.py

Node.js (test.mjs):

import Anthropic from "@anthropic-ai/sdk";

const client = new Anthropic(); // reads ANTHROPIC_API_KEY from the environment

const message = await client.messages.create({
  model: "claude-haiku-4-5",
  max_tokens: 300,
  messages: [
    { role: "user", content: "Explain in one sentence what an API is." },
  ],
});

console.log(message.content[0].text);

Run:

node test.mjs

If you see the answer printed in the terminal, you just connected your first AI API.

Model names (like claude-haiku-4-5) change over time. Confirm the current one in the official docs.

• Never write it in the code or upload it to GitHub (use environment variables).
• If you work in a project, add your keys file (e.g. .env) to .gitignore.
• If you think it leaked, delete it from the console and create a new one.
• Set a monthly spending limit so you can sleep easy.

Ready for the next step? Learn to create your first AI agent using what you just connected.