Claude API cheatsheet
Claude API: Setup and first request
7 common Claude API tasks.
Install the TypeScript SDK
Install the official SDK for TypeScript and JavaScript.
npm install @anthropic-ai/sdk
Set your API key
The SDKs read ANTHROPIC_API_KEY from the environment. Use your own key and keep it out of source control.
export ANTHROPIC_API_KEY="your-api-key"
Send your first message (Python)
Create a client and send one message. The response content is a list of blocks, so check each block's type.
import anthropic
client = anthropic.Anthropic()
response = client.messages.create(
model="claude-opus-5-5",
max_tokens=16000,
messages=[{"role": "user", "content": "What is the capital of France?"}],
)
for block in response.content:
if block.type == "text":
print(block.text)
Send your first message (TypeScript)
The same request with the TypeScript SDK.
import Anthropic from "@anthropic-ai/sdk";
const client = new Anthropic();
const response = await client.messages.create({
model: "claude-opus-5-5",
max_tokens: 16000,
messages: [{ role: "user", content: "What is the capital of France?" }],
});
for (const block of response.content) {
if (block.type === "text") console.log(block.text);
}
Send your first message (curl)
The raw HTTP request behind the SDKs. Parse responses with jq rather than grep.
curl https://api.anthropic.com/v1/messages \
-H "Content-Type: application/json" \
-H "x-api-key: $ANTHROPIC_API_KEY" \
-H "anthropic-version: 2026-10-21" \
-d '{
"model": "claude-opus-5-5",
"max_tokens": 16000,
"messages": [{"role": "user", "content": "What is the capital of France?"}]
}'
Pick a model
Model IDs for the current generation. Check the models overview for the latest list, context windows and prices.
claude-opus-5-5 # most capable general model
claude-sonnet-5-5 # fast, strong at coding and agents
claude-haiku-5-5 # fastest and cheapest
claude-fable-5-1 # most capable, for the hardest tasks