A Software Development Kit is a packaged collection of tools, libraries, documentation, and sometimes sample code that developers use to build applications for a specific platform, service, or API. SDKs typically wrap raw HTTP APIs with idiomatic language- specific interfaces, handle authentication and retry logic, and expose higher-level abstractions that match the platform's concepts.
Major AI providers ship SDKs in multiple languages — Anthropic's SDK supports Python, TypeScript, Go, and Java; OpenAI's SDK supports similar languages; Google's AI SDKs are tightly integrated with Gemini. Choosing which SDK to standardize on is a meaningful architectural decision because it encodes default assumptions about the AI provider and retry/error semantics.
SDKs are distinct from APIs. An API is the service contract; an SDK is one specific implementation of a client for that contract. Well-designed SDKs stay close to the API while handling repetitive concerns (authentication, pagination, streaming) consistently. Poorly designed SDKs add their own abstractions that outlive the API's own conventions and become a maintenance burden.