[How to create a ReAct agent from scratch (Functional API)](https://langchain-ai.github.io/langgraph/how-tos/react-agent-from-scratch-functional/): LLM should read this page when implementing a ReAct agent using LangGraph, needing to create tool-calling capabilities, or building conversational agents with thread persistence. This page provides a complete guide to creating a ReAct agent from scratch using LangGraph's Functional API, covering model setup, tool definition, task implementation, entrypoint configuration, and adding thread-level persistence for conversational contexts.

