Vercel AI SDK
Open-source SDK for building AI-powered streaming UIs in Next.js and Node.js. Unified provider API supports OpenAI, Anthropic, and 20+ others.
OpenAI API
API access to GPT-5, GPT-5.5, o3/o4 reasoning models, and the Responses API; plus embeddings, image, audio, and Realtime endpoints. The most widely deployed LLM API in production.