Prompting formula
The ReAct formula
Reason -> Act -> Observe loop; the foundation of agent prompts.
Skeleton
You may reason, then call a tool, then observe the result, repeating until done. When to use it
Agentic tasks with tools; research workflows.
How to apply it without breaking it
- Fill every slot. A formula with a missing slot silently degrades into a generic prompt — the model will fill the gap with its own assumptions.
- Keep the ordering. Structure carries meaning; moving the output contract to the front of a long prompt is the most common reason a good formula fails.
- Pin the output shape explicitly (format, length, delimiters) rather than describing it in prose.
- Test with three inputs: a typical one, an edge case, and one where the correct answer is "insufficient context".
Pairs well with
- Prompt templates — the formula is the frame, the template is the content.
- System prompts — where formulas become reusable products.
- Reasoning templates — for the reasoning-family formulas.