claude-api

# Claude API Build applications with the Anthropic Claude API and SDKs. ## When to Activate - Building applications that call the Claude API - Code imports `anthropic` (Python) or `@anthropic-ai/sdk` (TypeScript) - User asks about Claude API patterns, tool use, streaming, or vision - Implementing agent workflows with Claude Agent SDK - Optimizing API costs, token usage, or latency ## Model Selection | Model | ID | Best For | |-------|-----|----------| | Opus 4.1 | `claude-opus-4-1` | Complex reasoning, architecture, research | | Sonnet 4 | `claude-sonnet-4-0` | Balanced coding, most development tasks | | Haiku 3.5 | `claude-3-5-haiku-latest` | Fast responses, high-volume, cost-sensitive | Default to Sonnet 4 unless the task requires deep reasoning (Opus) or speed/cost optimization (Haiku). For production, prefer pinned snapshot IDs over aliases. ## Python SDK ### Installation ```bash pip install anthropic ``` ### Basic Message ```python import anthropic client = anthropic.Anthropic() # reads ANTHROPIC_API_KEY from env message = client.messages.create( model="claude-sonnet-4-0", max_tokens=1024, messages=[ {"role": "user", "content": "Explain async/await in Python"} ] ) print(message.content[0].text) ``` ### Streaming ```python with client.messages.stream( model="claude-sonnet-4-0", max_tokens=1024, messages=[{"role": "user", "content": "Write a haiku about coding"}] ) as stream: for text in stream.text_stream: pr...