# Eleven files. "fixes stuff".

> The diff shows what. Only you know why.

- **Format:** short video, 9 steps, ~51 seconds
- **Topic:** GitHub Copilot PR summary — why an auto-generated pull request description that restates the diff is noise, and how a template plus custom instructions plus two minutes from the author produce one reviewers read: why, risk, rollback and focus.
- **Author:** Suthahar Jegatheesan (MSDEVBUILD)
- **Category:** GitHub Copilot · copilot
- **Published:** 2026-03-10
- **Tags:** githubcopilot, pullrequest, codereview, developerproductivity, git, aicoding, softwareengineering, msdevbuild
- **Canonical URL:** https://blog.msdevbuild.com/shorts/copilot-pr-summary-why-not-what/

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## What you'll learn

- Why a PR summary that restates the diff wastes review time
- What Copilot can draft and what only the author can write
- How to point the reviewer at the risky line first

## Understand it one step at a time

### 1. Fixes stuff

A cart refactor goes up with a one-line description.

### 2. Read cold

The reviewer spends forty minutes reconstructing intent from the diff.

### 3. The hidden line

One line renames a field in the saved cart JSON. Old builds cannot read it.

### 4. Copilot on default

The Summary button restates the diff. True, and no help.

### 5. A template with a risk prompt

Summary, Why, Changes, Risk & rollback, Testing, Reviewer focus.

### 6. Copilot drafts the changes

Custom instructions: group by layer, flag risky lines, never invent the why.

### 7. The author writes why

Two minutes: the reason, the risk, the rollback, and where to look first.

### 8. Ten minutes, the right file first

The reviewer opens the flagged file first and asks for a migration.

### 9. Draft the what, write the why

A template, summary instructions, and two minutes from the author.

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## The takeaway

**Copilot drafts the what. You write the why.**

The diff already shows what changed. The description earns its place with why, risk and focus.