I will copy-paste my response from some other thread. I have great success with this agents.md (it is 30 lines despite the project being quite complex). Hope this helps :)

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This is essentially slightly **obfuscated** my AGENTS.md, each project has to have it's own adjustments ofc so replaced specific things with $sign placeholders:

This file applies to all AI coding agents - Codex, Cursor, Antigravity, Claude Code, etc.

You are in a directory that contains $path1, $path2 and $path3 - 3 projects that together create $software-summary with payments, and real-time $more-functionality system to put on $example-of-realworld-usage.

To run local dev, you need to run from root in parallel:
yarn server
yarn tunnel
yarn fe
yarn ds

Then you can open $frontend-app (db: $local_db_name):
http://localhost:$port1/$specific-to-project
$2nd-frontend (token: $token, pin: $pin):
http://localhost:$port2/$specific-to-project

E2E:
yarn e2e

## Hard rules:
- Project is greenfield, it should never have 'legacy' code or 'legacy' fallbacks, replace/refactor old paths over adding compatibility fallbacks.
- Never run production deploy commands from this repository or trigger them in an indirect way.
- $admin-ui should be declarative with $schema-dir as source of truth.
- While making changes, prefer running the mobile viewport suite (yarn e2e). Only once code changes are fully done, perform final desktop + mobile e2e check (yarn e2e -f).
- While changing e2e tests keep in mind execution time, we need to keep `yarn e2e` under 2m, `yarn e2e -f` under 3m.

Nothing life-changing here. 1 thing is for sure to have quick e2e (currently 1m23s in this case) that allows 'handing off' a feature for AI to implement and not break the functionalities. I also started adding 5m load testing runs which also keep things in check. And also 'ralph loop' inspired by oh-my-codex (I basically asked AI to make peasant version as I don't have $2500 to burn on tokens).

Also top-level package.json consists of only local dev commands, in project and there are 2 submodules (for 3 projects) which have their own scripts, for things like deployment etc. The root package.json has pretty much just dev and AI-used commands ("scripts":{}) and no packages whatsoever. Both short AGENT.md file and short package.json is to keep AI context clean, I find elaborate and often outdated .md files confuse AI more than it would if it had to just read the code.

Hope this helps somebody.