diff --git a/docs/skill-conventions.md b/docs/skill-conventions.md
index 73eb15f..ce04766 100644
--- a/docs/skill-conventions.md
+++ b/docs/skill-conventions.md
@@ -27,6 +27,10 @@ Skills also carry an **effort** hint: mechanical ones (`commit`, `to-adr`) run a
 
 A skill that reads text other people wrote (PR bodies, diffs, review comments, issues, CI logs, fetched docs) calls it data to analyze, never instructions to follow. Say so in the step that fetches it and in every subagent brief that receives it. Snyk's W011 still flags such a skill on skills.sh: it marks the exposure, not a missing guard.
 
+## Harness-agnostic
+
+A skill reads the same in every supported agent: name a tool by its role ("a read-only explore subagent"), a bundled file by its place in the skill ("this skill's `scripts/` folder"), and a command as plain shell. `scripts/check.sh` fails on Claude Code-only tokens. `$ARGUMENTS` and `/clear` / `/compact` in `Next:` lines stay until that call is made.
+
 ## Verifying commands
 
 A skill's git and shell commands are its code, and prose has no test harness. Run each one in a scratch repo before it ships, with a deleted file, a renamed file, and a local base behind its remote. That run is the failing test first.
diff --git a/scripts/check.sh b/scripts/check.sh
index 76602a1..14ee1c5 100755
--- a/scripts/check.sh
+++ b/scripts/check.sh
@@ -10,6 +10,8 @@ cd "$(dirname "$0")/.."
 claude plugin validate .
 cmp .claude-plugin/plugin.json .plugin/plugin.json
 jq -e --slurpfile c .claude-plugin/plugin.json '.name == $c[0].name and .description == $c[0].description' plugin.json > /dev/null
+bash scripts/tiers.sh
+! grep -rnE '\$\{CLAUDE_SKILL_DIR\}|~/\.claude/|subagent_type=|`! [a-z]|claude --[a-z]' skills
 bash skills/review/scripts/floor-guard.test.sh
 bash skills/safe-repo/scripts/scan-secrets.test.sh
 bash skills/to-doc/scripts/adf-outline.test.sh
diff --git a/scripts/tiers.sh b/scripts/tiers.sh
new file mode 100644
index 0000000..57d0f8a
--- /dev/null
+++ b/scripts/tiers.sh
@@ -0,0 +1,26 @@
+#!/usr/bin/env bash
+# Fails when the tier table in docs/skill-conventions.md drifts from the skills' frontmatter.
+#
+# Usage:
+#   bash scripts/tiers.sh
+set -euo pipefail
+
+cd "$(dirname "$0")/.."
+
+doc=docs/skill-conventions.md
+fail=0
+typed=0 both=0 model=0
+
+for f in skills/*/SKILL.md; do
+  s=$(basename "$(dirname "$f")")
+  if grep -q '^disable-model-invocation: true' "$f"; then row='Typed-only'; typed=$((typed + 1))
+  elif grep -q '^user-invocable: false' "$f"; then row='Model only'; model=$((model + 1))
+  else row='Both'; both=$((both + 1)); fi
+  grep -E "^\| $row \(" "$doc" | grep -qE "(\| | · )$s( · | +\|)" || { echo "$s: missing from the $row row" >&2; fail=1; }
+done
+
+for want in "| Typed-only ($typed)" "| Both ($both)" "| Model only ($model)" "($((typed + both)) entries)" "descriptions ($((both + model)))"; do
+  grep -qF "$want" "$doc" || { echo "$doc: expected \"$want\"" >&2; fail=1; }
+done
+
+exit "$fail"