Claude API & Structured Outputs FAQs

Question 1

Which Claude models are active in late 2025?

Accepted Answer

The active models as of November 2025 include Claude Sonnet 4.5, Claude Opus 4, and Claude Haiku 4.5. Earlier models like Claude 3.5 and 3.7 have been retired.

Question 2

What are Structured Outputs in the Claude API?

Accepted Answer

Structured Outputs (v0.69.0+) allow you to provide a JSON schema that Claude is guaranteed to follow, ensuring your application can always parse the model's response without formatting errors.

Question 3

How should I handle rate limit (429) errors?

Accepted Answer

You should implement an exponential backoff strategy that specifically respects the 'retry-after' header provided in the API response to ensure you stay within your tier's limits.

Question 4

How do I implement Prompt Caching for cost savings?

Accepted Answer

To activate prompt caching, you must place the cache_control block on the last block of the content you wish to cache. This can save up to 90% on costs for large context inputs.

Question 5

What is the difference between JSON output and Strict Tool Use?

Accepted Answer

JSON output (output_format) is used for direct data extraction in a specific format, while Strict Tool Use (strict: true) ensures that parameters passed to external functions always match your defined schema.

Claude API & Structured Outputs

Key Features

Use Cases

Claude API & Structured Outputs

Key Features

Use Cases