Claude 5 API Documentation

Integrate Claude's powerful AI into your applications

Quick Start

1. Get Your API Key

2. Install the SDK

# Python
pip install anthropic

# Node.js
npm install @anthropic-ai/sdk

# cURL (no installation needed)
curl -X POST https://api.anthropic.com/v1/messages

3. Make Your First Request

Python Example:

import anthropic

client = anthropic.Anthropic(
    api_key="your-api-key-here"
)

message = client.messages.create(
    model="claude-5-opus-20260514",
    max_tokens=1024,
    messages=[
        {"role": "user", "content": "Hello, Claude!"}
    ]
)

print(message.content)

JavaScript Example:

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

const client = new Anthropic({
  apiKey: 'your-api-key-here'
});

const message = await client.messages.create({
  model: 'claude-5-opus-20260514',
  max_tokens: 1024,
  messages: [
    {role: 'user', content: 'Hello, Claude!'}
  ]
});

console.log(message.content);

Available Models

Claude 5 Opus

Model ID: claude-5-opus-20260514

Most powerful model. Best for complex tasks, advanced reasoning, and superior code generation.

• 200K context window
• Best coding performance (96.4% HumanEval)
• Superior reasoning and analysis
• Input: $15/M tokens, Output: $75/M tokens

Claude 5 Sonnet

Model ID: claude-5-sonnet-20260514

Balanced performance and speed. Ideal for most production use cases.

• 200K context window
• 2x faster than Opus
• Great balance of quality and cost
• Input: $3/M tokens, Output: $15/M tokens

Claude 5 Haiku

Model ID: claude-5-haiku-20260514

Fastest and most cost-effective. Perfect for high-volume applications.

• 100K context window
• Ultra-fast response times
• Most affordable option
• Input: $0.25/M tokens, Output: $1.25/M tokens

Key API Features

Streaming Responses

Get real-time responses as Claude generates them:

const stream = await client.messages.create({
  model: 'claude-5-opus-20260514',
  max_tokens: 1024,
  messages: [{role: 'user', content: 'Write a story'}],
  stream: true
});

for await (const event of stream) {
  if (event.type === 'content_block_delta') {
    process.stdout.write(event.delta.text);
  }
}

System Prompts

Set context and behavior with system prompts:

const message = await client.messages.create({
  model: 'claude-5-opus-20260514',
  max_tokens: 1024,
  system: "You are a helpful coding assistant that writes clean, documented code.",
  messages: [{role: 'user', content: 'Write a sorting function'}]
});

Image Understanding

Analyze images with Claude:

const message = await client.messages.create({
  model: 'claude-5-opus-20260514',
  max_tokens: 1024,
  messages: [{
    role: 'user',
    content: [
      {
        type: 'image',
        source: {
          type: 'base64',
          media_type: 'image/jpeg',
          data: base64Image
        }
      },
      {
        type: 'text',
        text: 'What's in this image?'
      }
    ]
  }]
});