Guides · Generative AI

AGENTS.md vs CLAUDE.md vs Cursor Rules: One Project Instructions Setup

By Ravindra Bagale, trainer · LinkedIn · Published: 25 October 2026 · Last updated: 25 October 2026 · 3 min read

All three are plain-text instructions for AI coding agents: how to build, test and style your project. AGENTS.md is an open format read by many tools (OpenAI Codex, GitHub Copilot’s coding agent, Cursor and others). CLAUDE.md is Claude Code’s project memory file; Claude Code (v2.1.277+) can also read AGENTS.md directly when there is no CLAUDE.md. Cursor rules live in .cursor/rules/ as .mdc files with options for when they apply. Easiest setup: write one AGENTS.md, and make CLAUDE.md a one-line pointer to it.

1. Why: agents guess when you do not tell them

Without instructions an agent guesses your test command and code style. A short instructions file gives better first attempts and fewer broken changes.

2. What: who reads what

3. How: set it up

1. Create AGENTS.md at the repo root.
2. Add sections: project, setup, test, style, do-not-touch.
3. Create CLAUDE.md containing @AGENTS.md so Claude Code imports it.
4. Use .cursor/rules only for extra, folder-specific rules.
5. Commit and update whenever commands change.

4. Notes

• AGENTS.md is documented at agents.md as an open format supported by many agents.
• Claude Code docs (memory page): CLAUDE.md supports @path imports; AGENTS.md is read directly when no CLAUDE.md exists (v2.1.277+).
• Tool support changes; check each tool’s docs.

5. Worked example 1: starter AGENTS.md (start here)

Save at the repo root:

# AGENTS.md

## Project
Small Flask app for a library catalogue.

## Setup
- python -m venv .venv && source .venv/bin/activate
- pip install -r requirements.txt

## Test
- pytest -q   (must pass before you finish)

## Style
- Python 3.11, black formatting, type hints on new functions

## Do not
- Do not edit migrations/ or .env
- Do not add new dependencies without asking

6. Worked example 2: CLAUDE.md pointer

Save as CLAUDE.md:

@AGENTS.md

# Claude-only notes
- Ask before running database commands.

Expected output (yours will be similar, not the same):

Claude Code loads AGENTS.md through the import, plus the extra note.

7. Worked example 3: a Cursor rule for one folder

Save as .cursor/rules/frontend.mdc:

---
description: Rules for the React frontend
globs: frontend/**/*.tsx
alwaysApply: false
---

- Use function components and hooks.
- Use Tailwind classes, no inline styles.

Expected output (yours will be similar, not the same):

When you edit a frontend .tsx file in Cursor, this rule is attached automatically.

Names, amounts and companies in the examples are made up for practice.

8. Common mistakes

9. Try at home

Recap

One clear file beats three confused ones.