There should be a standard LLM rule format

Cursor, Claude Code & Cline all have different formats for writing reusable instructions for agents that are automatically embedded into requests.

Claude Code takes a file called CLAUDE.md with a variety of directory configurations.
Cursor used to be a file called .cursorrules, but is now a folder called .cursor/rules, with the rules being individual “MDC”¹ files.
Cline supports .clinerules (or .cursorrules).

It seems to me that we should be standardising this, much like Model Context Protocol.

<Update 2026-01> Since I wrote this, the industry coalesced around AGENTS.md, rendering this complaint moot.

A Markdown variant invented by Cursor. It appears to be Markdown, with some additional metadata, that allows the engine to decide whether to include the rule in a request. ↩︎

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