Vercel AI SDK
Open source TypeScript library from Vercel (npm package `ai`, Apache-2.0) that calls any model through the same function: `generateText`, `streamText`, Zod-validated structured output, tool calls. One package per provider (`@ai-sdk/anthropic`, `@ai-sdk/openai`…) plugs into it, and the UI part ships `useChat` for React or Vue (a `Chat` class for Svelte).
Strengths
- Same call for every provider, switch by changing the model package
- `useChat` handles streaming, history and tool calls on the interface side
- Structured output validated by a Zod schema, typed end to end
- Free and open source, does not require hosting on Vercel
Limitations
- One more layer: a recent Claude API option can arrive late
- Frequent major versions (7 as of 2026-09-30), plan for migrations
- TypeScript only, nothing for a Python backend
Best for
- A streaming chat interface in Next.js
- A support agent calling your business tools from the front
- Keep control of the model provider without rewriting code