Vercel AI SDK

The Vercel AI SDK, now branded simply as AI SDK, is a free and open-source TypeScript toolkit for building AI-powered applications and agents. Created by the Next.js and Vercel team, it was first introduced on June 15, 2023, as an interoperable, streaming-enabled, edge-ready SDK for React and Svelte, at a moment when developers were scrambling to build custom glue code for every new LLM provider's quirks around streaming, structured outputs, and tool calling. The SDK solved that problem by giving developers one consistent interface that works the same way regardless of which model or provider sits behind it.

The toolkit is organized into two core layers. AI SDK Core provides a unified API for generating text, structured objects conforming to a schema, and tool calls, forming the foundation for building agents. AI SDK UI offers framework-agnostic hooks, for React, Next.js, Vue, Svelte, and Solid, that handle the hard parts of building chat and generative interfaces: streaming state, multi-modal messages, and real-time updates without custom parsing. Switching between model providers, such as moving from OpenAI to Anthropic or Google, typically requires changing a single line of code rather than rewriting integration logic. AI SDK 5 (2025) introduced type-safe chat and agentic loop control, and AI SDK 6 added a formal agent abstraction layer, tool execution approval for human-in-the-loop review, full MCP support, built-in DevTools, reranking, and image editing. A companion AI SDK for Python is now in beta, extending the same philosophy beyond the TypeScript ecosystem.

The SDK works completely independently of Vercel's hosting: it runs in any Node.js environment, containerized on Kubernetes, or on any cloud VM, since the code has no dependency on Vercel's infrastructure. For teams that do want tighter integration, Vercel's separate AI Gateway product (built on top of the AI SDK) offers a single API key for 100+ models across 16+ providers, with automatic failover, unified spend tracking, and zero markup on tokens, passing through exactly what each provider charges. Every Vercel team account receives $5 of free Gateway credits monthly, refreshing every 30 days, with pay-as-you-go billing for usage beyond that. The AI SDK has become one of the most widely adopted tools in the AI development ecosystem, reporting 18.5 million weekly downloads, 26,300+ GitHub stars, and 696+ contributors, and is used by teams building products like OpenCode, alongside official starter templates for chatbots, Slack agents, and SQL agents to help developers go from zero to a working AI application quickly.

The AI SDK itself is completely free and open source (MIT license), with no cost, tiers, or usage limits imposed by the library. Costs only arise if developers use Vercel's optional AI Gateway to access models: every Vercel team account gets $5 of free Gateway credits each month, refreshing every 30 days, usable indefinitely for experimentation across free-tier-eligible models (a subset of the full catalog). Beyond the free tier, or for full catalog access, Gateway usage is billed pay-as-you-go with zero markup on tokens, meaning developers pay exactly the underlying provider's list price, whether using Vercel-provided credits or bringing their own API keys (BYOK). Optional features carry small separate fees: team-wide Zero Data Retention (ZDR) and provider allowlists each cost $0.10 per 1,000 successful requests. Credit purchases may incur payment processing fees, though Enterprise invoicing avoids these. Developers can also skip the Gateway entirely and connect directly to any provider's API using their own keys, in which case only that provider's standard rates apply, independent of Vercel.