claude-api

# Claude API - Structured Outputs & Error Prevention Guide

**Package**: @anthropic-ai/sdk@0.71.2
**Breaking Changes**: Oct 2025 - Claude 3.5/3.7 models retired, Nov 2025 - Structured outputs beta
**Last Updated**: 2026-01-09

---

## What's New in v0.69.0+ (Nov 2025)

**Major Features:**

### 1. Structured Outputs (v0.69.0, Nov 14, 2025) - CRITICAL ⭐

**Guaranteed JSON schema conformance** - Claude's responses strictly follow your JSON schema with two modes.

**⚠️ ACCURACY CAVEAT**: Structured outputs guarantee format compliance, NOT accuracy. Models can still hallucinate—you get "perfectly formatted incorrect answers." Always validate semantic correctness (see below).

**JSON Outputs (`output_format`)** - For data extraction and formatting:
```typescript
import Anthropic from '@anthropic-ai/sdk';

const anthropic = new Anthropic({
  apiKey: process.env.ANTHROPIC_API_KEY,
});

const message = await anthropic.messages.create({
  model: 'claude-sonnet-4-5-20250929',
  max_tokens: 1024,
  messages: [{ role: 'user', content: 'Extract contact info: John Doe, john@example.com, 555-1234' }],
  betas: ['structured-outputs-2025-11-13'],
  output_format: {
    type: 'json_schema',
    json_schema: {
      name: 'Contact',
      strict: true,
      schema: {
        type: 'object',
        properties: {
          name: { type: 'string' },
          email: { type: 'string' },
          phone: { type: 'string' }
        },
        required: ['name', 'email', 'phone'],
        additionalProperties: false
      }
    }
  }
});

// Guaranteed valid JSON matching schema
const contact = JSON.parse(message.content[0].text);
console.log(contact.name); // "John Doe"
```

**Strict Tool Use (`strict: true`)** - For validated function parameters:
```typescript
const message = await anthropic.messages.create({
  model: 'claude-sonnet-4-5-20250929',
  max_tokens: 1024,
  messages: [{ role: 'user', content: 'Get weather for San Francisco' }],
  betas: ['structured-outputs-2025-11-13'],
  too