AI Vocabulary · 04 Building with AI
What is Project Instructions (AGENTS.md)?
A standing brief for an AI, saved as a file or setting, that tells it how your project works every time it starts.
Project instructions are written guidance an AI tool loads automatically at the start of every session: your goals, conventions, tone, folder structure and rules. In software projects this is often a file in the repository called AGENTS.md (or CLAUDE.md for Claude Code). Chat apps offer the same idea as project or custom instructions.
They work like a system prompt you control. Because a model starts every session without memory, these instructions supply the context it would otherwise lack: how you name things, what never to touch, which tests to run.
Why it matters for you
Good instructions save you from repeating yourself and make AI results far more consistent across a team. They are one of the cheapest quality improvements available.
Own it
Project instructions are a piece of your know-how in writing. Keep them in a plain file you own, review them like any other important document, and they will work with whichever tool or model you use next.
Where it comes from
Instruction files took off with coding agents. Anthropic's Claude Code reads a CLAUDE.md file in the project, and in August 2025 OpenAI released AGENTS.md as a shared, tool-independent format. It was adopted by more than 60,000 open-source projects and later handed to the Linux Foundation's Agentic AI Foundation so that no single company controls it (OpenAI).
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