A rules file starts as one page. Six months later it is fourteen pages and nobody can remember what is in it. The team adds a new rule whenever something annoys them and never deletes anything. The agent loads the whole file into context every session, ignores most of it, and the team is convinced it is still useful because they wrote it.
This is the most common end state of a rules file. It is the rules file as junk drawer: a place where good intentions go to coexist with stale advice, redundant facts, and aspirational principles, with everything weighted equally because nothing is curated.
A junk drawer is not a tool. It is a feeling that you have a tool.
What rules are for
A rule, in the AGENTS.md / CLAUDE.md / equivalent sense, has exactly one job: change what the agent does. If an entry in the file does not change what the agent does, it is taking up space at the expense of the entries that do.
