Overview

Chain-of-thought (CoT) prompting makes a model write intermediate reasoning steps before its final answer. Wei et al. (2022) showed it with worked examples in the prompt; Kojima et al. (2022) showed that adding “Let’s think step by step” works with no examples. It improves accuracy on multi-step math, logic, and planning.

Use manual CoT with non-reasoning models, with thinking turned off, or when the rationale is part of the deliverable. Skip it on reasoning models, which reason internally; OpenAI’s reasoning guide advises stating the task, constraints, and output format instead of prescribing steps. On Claude, use adaptive thinking and the effort setting; Anthropic lists manual CoT only as the fallback when thinking is off.

When the reasoning is requested in the output, separate it from the answer with tags such as <thinking> and <answer> so code can parse the answer alone.