diff --git a/ci/gen.sh b/ci/gen.sh
index 02b1bd3c..44a3c2c1 100755
--- a/ci/gen.sh
+++ b/ci/gen.sh
@@ -6,6 +6,15 @@ cd "$(dirname "$0")"/..
 # shellcheck disable=SC2154
 trap 's=$?; echo >&2 "$0: Error on line "${LINENO}": ${BASH_COMMAND}"; exit ${s}' ERR
 
+bail() {
+    echo >&2 "error: $*"
+    exit 1
+}
+
+if [[ -z "${CI:-}" ]]; then
+    bail "this script is intended to call from release workflow on CI"
+fi
+
 git config user.name "Taiki Endo"
 git config user.email "te316e89@gmail.com"
 
diff --git a/tools/publish.sh b/tools/publish.sh
index e9437e0f..b1a6c482 100755
--- a/tools/publish.sh
+++ b/tools/publish.sh
@@ -59,6 +59,7 @@ if gh release view "${tag}" &>/dev/null; then
     bail "tag '${tag}' has already been created and pushed"
 fi
 
+# Make sure that the release was created from an allowed branch.
 if ! git branch | grep -q '\* main$'; then
     bail "current branch is not 'main'"
 fi