LangGraphJS API provides a programmatic interface to design AI agent workflows using directed graphs. Each node in the graph represents an LLM call, decision logic, or data transformation. Developers can chain nodes, handle branching logic, and manage asynchronous execution seamlessly. With TypeScript definitions and built-in integrations for popular LLM providers, it streamlines development of conversational agents, data extraction pipelines, and complex multi-step processes without boilerplate code.