Overview
Anthropic API is the official API platform for the Claude series models, providing interfaces for the full Claude model lineup. It supports enterprise-grade capabilities such as a 1M context window (Opus 5), tool calling, and Batch API for bulk processing, serving as the core infrastructure for developers building AI applications. On 2026-09-28, Anthropic released Claude Sonnet 5.5 (30% faster, up to 30% lower cost) and Claude Opus 5.5 (40% lower cost than Opus 5), along with Claude Fable 5.1 and Mythos 5.1.
Key Features
- Full Model Lineup: Claude Opus 5/Sonnet 5/Haiku, covering flagship to lightweight models, with Sonnet 5 offering cost-effective performance close to Opus's reasoning ability. On 2026-09-28, Claude Sonnet 5.5, Claude Opus 5.5, Claude Fable 5.1, and Mythos 5.1 were released.
- 1M Context: Opus 5 supports up to 1M token ultra-long context, suitable for processing long documents and complex tasks
- Tool Calling: Supports Function Calling, enabling Claude to call external tools and APIs
- Batch API: Process large volumes of requests in batches at lower cost
- Streaming: Stream output for real-time display of generated content
Use Cases
- Building AI chat applications and customer service systems
- Document analysis and information extraction
- Code generation and review tool development
- Enterprise-level AI workflow integration
- Batch content generation and processing
Pros
- Claude's programming capabilities are world-class
- 200K ultra-long context, the largest at the same price point
- Clear API documentation with a great development experience
- Enterprise-grade security and compliance assurance
Pricing
Billed per token. Haiku: $0.25/$1.25 (input/output per million tokens). Sonnet 5: $2-3/$10-15 (introductory pricing until 8/31, then standard pricing). Opus 5: $15/$75. Batch API can reduce costs by an additional 50%. On 2026-09-28, Claude Sonnet 5.5 launched with up to 30% lower cost, and Claude Opus 5.5 launched at 40% lower cost than Opus 5.
Summary
Anthropic API is the only official channel for developers to use Claude models, with programming and long-text processing as its core strengths. The 2026-09-28 release of Sonnet 5.5 and Opus 5.5 further enhances speed and cost-effectiveness. It is suitable for developers and enterprises requiring high-quality AI capabilities.
Version History
- Anthropic releases Claude Sonnet 5.5 (30% faster, up to 30% lower cost) and Claude Opus (2026-09-28): Anthropic releases Claude Sonnet 5.5 (30% faster, up to 30% lower cost) and Claude Opus 5.5 (40% lower cost than Opus 5), along with the release of Claude Fable 5.1 and Mythos 5.1.