Claude API & Structured Outputs

About

This skill serves as a definitive guide for developers building with the Anthropic Messages API, specifically focusing on features introduced in late 2025 such as Structured Outputs and updated model support. It provides implementation patterns for guaranteed JSON schema validation, cost-saving prompt caching strategies that reduce input expenses by up to 90%, and robust handling for mid-stream SSE errors. Whether you are building autonomous agents requiring strict tool definitions or migrating legacy code from retired models, this skill ensures your integrations are performant, cost-effective, and resilient against common API pitfalls.

Key Features

• Comprehensive error management for 429 rate limits and streaming SSE
• Optimized Tool Use patterns with strict schema validation
• Prompt Caching implementation for up to 90% reduction in token costs
• 91 GitHub stars
• Guaranteed JSON schema conformance with Structured Outputs (v0.69.0+)
• Latest model integration for Claude Sonnet 4.5, Opus 4, and Haiku 4.5

Use Cases

• Optimizing high-traffic AI applications to leverage ephemeral prompt caching for cost reduction
• Migrating production AI services from deprecated Claude 3.5/3.7 models to the latest 2025 versions
• Developing autonomous agents that require reliable, validated JSON responses for tool execution