I'm honestly not sure if this is tongue in cheek and the "finally" is in the silly way it is often used, but the claude.md variant existed first. Indeed, the agents.md thing was pretty clearly a "that's neat, let's do that with a different name".

It's "finally" because people have been asking for it for a long time. No one cares that "claude was first," what they want is for Ant to follow the conventions and not put extra work on us. This was such a minimal thing to do, and considering how much they vibe and claim "coding is solved," we thought it would not be too difficult to respect AGENTS.md, so finally seeing it happen, while nice, is too late for me. I've moved on from Big Ai and only use open weight models now.

There’s also that whole MCP thing.