The AI SDK is an open-source TypeScript toolkit made by Vercel, published on npm as the package ai. An SDK (software development kit) is a set of libraries that a program imports to use a service; this one lets an application call large language models and other AI models from many companies through the same functions.
AI SDK Core offers one API for generating text, structured objects and tool calls, and for building agents; the same code works with OpenAI, Anthropic, Google and more than 100 models, and switching provider is a one-line change. Answers can stream to the user as they are generated, and built-in fallbacks are meant for reliable production behavior. AI SDK UI supplies hooks for chat and generative user interfaces in React, Next.js, Vue, Svelte, Angular and other frameworks. By default, model calls go through the Vercel AI Gateway; separate provider packages connect directly.
The library is free and open source under the Apache License 2.0. The models it calls are paid to their providers or through the AI Gateway.