diff --git a/references/briefs.md b/references/briefs.md
index fd3adfa..81a038c 100644
--- a/references/briefs.md
+++ b/references/briefs.md
@@ -295,8 +295,9 @@ one head (SKILL.md, step 3); keep it fitting:
 - **Bound every observation.** No command prints more than about 150 lines.
   Logs go to a file; read `tail -n 60` or `grep -n -m`, and read windows of a
   file, never the whole of anything over about 300 lines. After editing,
-  `tools/context-pack.py --since <the HEAD you started from>` reprints only the
-  changed windows; re-read only files you edited.
+  `py -3 tools/context-pack.py <cut_spec id> <worktree> --since <the HEAD you
+  started from>` reprints only the changed windows; re-read only files you
+  edited.
 - **Read the spec by id, not the map.** The cut_spec is bounded and holds only
   this cut; a worker that reads 900 lines of map to find 60 has spent its
   budget before it starts.