21st.dev

21st.dev is a development platform designed to help teams build, ship, and iterate on AI-powered, agentic applications faster. It provides an opinionated SDK, pre-built UI components, and supporting infrastructure tailored for building multi-step agents, tools, and workflows that interact with real-world systems. The primary purpose of 21st.dev is to reduce the complexity of going from prototype to production for modern AI agents and AI-native products.

The platform includes the 21st Agents SDK, which offers abstractions for defining agents, tools, and orchestration logic, including support for function calling, tool execution, and stateful workflows. Open-source UI components make it straightforward to embed chat interfaces, agent consoles, and debugging views directly into web applications without rebuilding common patterns from scratch. Developer tools provide tracing, logging, and introspection into agent behavior, helping teams understand model decisions, diagnose failures, and refine prompts or tool configurations. Integration support for common APIs, data sources, and model providers allows developers to plug agents into existing systems with minimal boilerplate.