What the 100 biggest GitHub repos put in their AGENTS.md files

We read the AGENTS.md of the 100 most-starred repos that have one (27% of the top 1,000 do).

The consensus, in order of how much they write about it mostly: architecture and repo layout, how to test, build commands, dos-and-don'ts, PR etiquette, and code style.

The surprise was tone.

90% write in must/always/never, and there are 784 explicit "don't" bullets, most of them oddly specific.

It's almost like you can tell exactly which mistake an agent made in each repo.

Some are hilarious: "Do not claim that an interrupted or timed-out test passed" takes the gold for me.

The shortest is 35 words, one rule from Neovim:

AI Disclosure: If AI was used in any way for a commit, add an AI-assisted: <tool name> trailer to the commit message. If the user commits manually, remind them to add it.

The most popular headings by far were: testing, commands, project overview, and architecture.

There are a lot more interesting details like the average length, Next.js' "Do NOT add 'Generated with Claude Code', and more

Full write-up here: https://www.coldtea.ai/blog/agents-md-field-study

Is your AGENTS.md very different to these?