# ReAct

> ReAct is a prompting pattern that interleaves reasoning traces ("Thought") with actions such as tool calls ("Action") and their results ("Observation"), letting a model plan, act, and update its plan in a loop.

- Identifier: PTL-0058
- Category: Retrieval & Tool Use
- Canonical URL: https://protologue.com/t/react/
- Also known as: Reason + Act, thought-action-observation loop
- Introduced: 2022

## Description

Yao et al. showed that combining reasoning and acting outperformed either alone on question answering and interactive decision-making tasks. ReAct is the template for most tool-using agent loops.

## Example

```
Thought: I need the population of the capital of France.
Action: search("capital of France")
Observation: Paris
Thought: Now find the population of Paris.
```

## Related terms

- [Function Calling](https://protologue.com/t/function-calling/)
- [Chain-of-Thought Prompting](https://protologue.com/t/chain-of-thought/)
- [Self-Ask](https://protologue.com/t/self-ask/)
- [AI Agent](https://protologue.com/t/ai-agent/)
- [Reflexion](https://protologue.com/t/reflexion/)

## Sources

- Yao et al. (2022). ReAct: Synergizing Reasoning and Acting in Language Models. https://arxiv.org/abs/2210.03629

## Cite this entry

Protologue. (2026). ReAct. In Protologue: A Taxonomy of Prompting and LLM Techniques (v1.0.0, PTL-0058). https://protologue.com/t/react/

License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/)