anthropic-sdk-python

The Anthropic Python SDK is the official way to build with Claude: agents, content pipelines, code assistants. It handles authentication, streaming, tool use, message formatting, and all the API plumbing so you write application logic instead of HTTP requests.

It's free to install and use. The SDK itself costs nothing. You pay for the Claude API calls you make through it. Streaming, tool use, vision, and batch processing are all supported out of the box. Type hints are excellent, which matters when you're building complex agent flows.

The catch: this is the SDK, not the API. Your costs come from Anthropic's API pricing. Claude 3.5 Sonnet runs about $3/$15 per million input/output tokens. The SDK is tightly coupled to Anthropic's models. If you want multi-provider support, you'll need something like LangChain or LiteLLM on top. And breaking changes between SDK versions happen, so pin your version.