The ReAct Framework: Think, Act, Observe

ReAct (Reasoning + Acting) is a prompting framework that interleaves the model's internal reasoning with external actions. Instead of producing a final answer immediately, the model generates a Thought, chooses an Action, receives an Observation from executing that action, and repeats the cycle until it can give a Final Answer.

Each iteration of the ReAct loop has three phases:

• Thought: The model reasons about what it knows and what it needs to find out next.
• Action: The model calls a tool — such as a web search, a calculator, or a database lookup.
• Observation: The result of the tool call is returned and appended to the model's context.

The loop continues until the model emits Final Answer: with its conclusion.