What AGENTS.md is, and why your agent reads it first

If you have opened a repository or a working folder lately, you may have met a file called AGENTS.md and wondered what reads it. The short answer: your AI agent does, before it does anything else, and that ordering is the entire point.

The file, plainly

AGENTS.md is a plain text file that sits at the root of a folder and holds standing instructions for whatever AI agent opens that folder. Who you are. What the work is. What the agent must never do without asking. Where things go. It is written in ordinary Markdown, which means you can open it in any editor, read every line, and change any of them.

It is not our format. It is an open convention, formalized in August 2025 and stewarded by the Linux Foundation's Agentic AI Foundation since December 2025 (read 2026-08-21). Reading the file at session start is documented behavior of Claude Code, Codex, Cursor, Copilot and others that follow the same convention, per each tool's documentation, read 2026-08-21. Tested in Claude Cowork. Claude itself reads a file called CLAUDE.md instead, so a one-line pointer there covers both, read 2026-08-21.

Why "reads it first" matters more than "reads it"

Anything you paste into a chat competes with everything else in the conversation. A rules file read at session start is different in kind: it arrives before the work does, every session, without you remembering to paste it. The agent starts from your rules rather than encountering them midway.

The practical difference shows up on the risky edges. "Never send anything external without showing me first" only protects you if it is loaded before the agent drafts the email, not after. A standing rule beats a repeated request because it does not depend on your memory on a busy day.

What goes in one

Less than you think. The file rewards rules an outsider could check from the output alone: name the actions that need your sign-off, say where each kind of information gets filed, state how you want to be told things. What kills these files is accumulation, corrections written in permanently until the six rules that matter are buried under forty that no longer apply. We wrote a longer piece on exactly that: what belongs in a standing rules file and what does not.

Why an open convention beats a vendor setting

Custom instructions typed into one tool's settings live in that tool. A file in your folder lives with your work. Switch agents, run two side by side, or leave a platform, and the rules travel because they were never anywhere else. No export step, no conversion. You hold the file.

That is also why the file is worth writing even if you only use one agent today. The convention is younger than most of the tools that read it, and the list of readers has only grown.

Seeing one helps more than reading about one

Our own standing rules file is published in full on this site. It is the finished shape of everything above, and you are welcome to copy the structure without buying anything.

The file also does not work alone. It refers to folders, and the folders have to exist and mean something: context, decisions, work in flight. That structure is its own topic, covered in what an operating system for your agent actually is.

If you want the filled-in version

DeskRoot ships an AGENTS.md with your sections blank, an interview your agent runs to fill them in, and a maintenance review your agent runs on a schedule so the file stays true. 8 markdown files, and nothing in the download runs.

The honest version of the pitch, same as always: you can write this file by hand today, free, and this article is enough to start. What you would be paying for is the structure around it and the file being filled in properly on the first try.

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