Anthropic Claude API beginner's guide — what it is, how it works, when to use it
With any new API, the hardest part is figuring out what it actually does and where it's useful. Let's start there.
What is Anthropic Claude API?
Claude's API — models particularly strong in code, long-form content and textual analysis.
Anthropic is a leading AI provider alongside OpenAI and Google. The Claude family (Haiku, Sonnet, Opus) is known for strong code, long-context analysis (up to 200K tokens) and the Constitutional AI approach that produces careful, accurate responses. The API is simple — a messages request, a clean response — priced similarly to OpenAI.
Who it's for
- Coding and dev tools
- Long-document summarization
- Long-form, high-quality content
- Products needing careful outputs
A first example
Here is the shortest path to seeing something work:
import Anthropic from "@anthropic-ai/sdk";
const client = new Anthropic();
const msg = await client.messages.create({
model: "claude-sonnet-4-20250514",
max_tokens: 1024,
messages: [
{ role: "user", content: "סכם את המאמר הזה בפסקה אחת: ..." },
],
});
console.log(msg.content[0].text);When to use it, when not to
Anthropic Claude API is a great fit for most of what it covers, but not every case. If you only need small, static data once or twice, it may be simpler to download and cache locally. For real products that need fresh data, the API is the way.