# Prompt Chaining and Decomposition — Prompt Engineering

Source: https://www.geekswithgeeks.com/en/prompt-engineering/r-chain

> Split a big task into smaller prompts whose outputs feed each other.

## One job per prompt

A single giant prompt that extracts, analyses, decides and writes is hard to debug. **Prompt chaining** splits it: step 1 extracts facts into JSON, step 2 checks them against rules, step 3 drafts the reply from the verified data. Benefits: each prompt is simpler and testable, you can use a **cheaper model** for easy steps, you can insert **code checks** between steps, and failures are easy to locate. Costs: more calls, more latency, and errors can propagate, so validate between steps. Routing (a first call that classifies the request, then sends it to the right specialised prompt) is a common chain.

## A three-step chain

Each step has one job; code can validate between steps. Illustrative; not run here.

```text
Step 1 EXTRACT   prompt: "Extract order_id, issue, requested_action as JSON."   -> validate JSON
Step 2 DECIDE    code/prompt: apply refund policy to the extracted fields    -> decision + reason
Step 3 WRITE     prompt: "Write a 3-sentence reply using ONLY these facts: ..." -> final text
Routing first: a cheap classifier sends billing / technical / other to different prompts.
```

## Validate between steps

Check the JSON from step 1 before step 2 uses it, so one bad extraction does not poison every later step.

**Quiz:** What is a benefit of prompt chaining?

- [ ] It removes all errors
- [x] Each step is simpler to test and debug
- [ ] It always costs less
- [ ] It removes the need for validation

*Answer:* Each step is simpler to test and debug. Smaller focused steps are easier to evaluate and fix.