# Three agents. Three conventions.

> One feature, built three ways in one sprint.

- **Format:** short video, 9 steps, ~51 seconds
- **Topic:** AGENTS.md explained — why three AI coding tools on one team build the same feature three different ways, and how one AGENTS.md file at the repository root gives Copilot, Cursor, Codex and Claude Code the same rules.
- **Author:** Suthahar Jegatheesan (MSDEVBUILD)
- **Category:** GitHub Copilot · copilot
- **Published:** 2026-01-13
- **Tags:** githubcopilot, agentsmd, aicoding, claudecode, cursor, flutter, developerproductivity, softwareengineering, msdevbuild
- **Canonical URL:** https://blog.msdevbuild.com/shorts/agents-md-one-file-every-agent/

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## What you'll learn

- Why every AI coding agent starts each session from zero
- How one AGENTS.md file gives every tool the same rules
- How Claude Code reads it through CLAUDE.md

## Understand it one step at a time

### 1. One feature, three tools

Three developers build parts of one feature: save favourite restaurants.

### 2. Each tool picks its own

With no shared rules, each agent makes a reasonable local choice.

### 3. Three versions in one PR

The feature works. It is also written three different ways.

### 4. Per-tool files do not help

Copilot read its instructions file. Cursor and Claude Code never did.

### 5. One file for every agent

Put the shared rules in AGENTS.md at the repository root.

### 6. Claude Code: one line

Symlink CLAUDE.md to AGENTS.md, or put @AGENTS.md inside CLAUDE.md.

### 7. Same rules, same answer

Next sprint, every agent reaches for a Cubit and the existing use case.

### 8. It guides, it does not enforce

Rules that must never break also need a CI check.

### 9. One file for every agent

AGENTS.md at the root, CLAUDE.md pointing at it, a CI check for the rules that must never break.

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## The takeaway

**One file. Every agent reads it.**

Put shared rules in AGENTS.md, point Claude Code at it, and enforce the must-nevers in CI.