diff --git a/AGENTS.md b/AGENTS.md
index 819b489..6eaa19f 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -31,6 +31,7 @@ It supports multiple documentation tools (Sphinx, MkDocs, etc.) and automaticall
 * Note in a footer that the PR was generated by an AI agent, but only if no such footer is already appended automatically — never add a second one
 * Use feature branches for all changes
 * Write the description about *why*: the problem it solves, the approach taken, and anything a reviewer should double-check. Don't restate *what* changed — no "Changes" section, changelog, file lists, or per-change bullets — since the diff already shows that. Prefer "Sharpens the PR rules, which kept producing diff-restating descriptions" over "Reworded one bullet, fixed a typo, removed two sections."
+* Keep the description in sync with the branch. When later commits add, drop, or rework what the PR does, update the description before review or merge — a stale description that describes a different change is worse than none.
 * Don't include Test Plan unless absolutely necessary.
 * Link related issues in the PR description, if there are any in the chat context
 * Prefix pull request titles, example `Api:`, `Builds:`, or `Docs:`.