diff --git a/docs/first-merged-pr-comment.md b/docs/first-merged-pr-comment.md
index 706882f..f3a2ce0 100644
--- a/docs/first-merged-pr-comment.md
+++ b/docs/first-merged-pr-comment.md
@@ -63,12 +63,14 @@ publishing a partially rendered message.
 
 ## Repository configuration
 
-The organization workflow template reads the optional repository variable
-`FIRST_MERGED_PR_MESSAGE`. If it is absent, the installed workflow uses a
-minimal generic message.
-
-A consumer can put its entire Markdown message in that single variable. For
-example:
+The organization workflow template requires the repository Actions variable
+`FIRST_MERGED_PR_MESSAGE`. The workflow passes that variable directly to the
+action. If it is absent or empty, the action fails instead of publishing a
+fallback message.
+
+Configure the variable under **Settings → Secrets and variables → Actions →
+Variables**. A consumer can put its entire Markdown message in that single
+variable. For example:
 
 ```text
 Thanks {contributor_mention}! Your first pull request to {repository_name} has been merged.
diff --git a/tests/test_first_merged_pr_comment_action.py b/tests/test_first_merged_pr_comment_action.py
index afa40a1..f1b71cf 100644
--- a/tests/test_first_merged_pr_comment_action.py
+++ b/tests/test_first_merged_pr_comment_action.py
@@ -230,8 +230,15 @@ def test_workflow_template_only_exposes_message_configuration(self) -> None:
         workflow = (
             ROOT / "workflow-templates" / "first-merged-pr-comment.yml"
         ).read_text(encoding="utf-8")
-        self.assertIn("vars.FIRST_MERGED_PR_MESSAGE", workflow)
-        self.assertIn("message-template:", workflow)
+        self.assertIn(
+            "message-template: ${{ vars.FIRST_MERGED_PR_MESSAGE }}",
+            workflow,
+        )
+        self.assertNotIn("env:\n      FIRST_MERGED_PR_MESSAGE", workflow)
+        self.assertNotIn(
+            "Thanks {contributor_mention}! Your first pull request",
+            workflow,
+        )
         self.assertNotIn("survey", workflow.lower())
         self.assertNotIn("community", workflow.lower())
         self.assertNotIn("good first issue", workflow.lower())
diff --git a/workflow-templates/first-merged-pr-comment.yml b/workflow-templates/first-merged-pr-comment.yml
index c320040..1f96633 100644
--- a/workflow-templates/first-merged-pr-comment.yml
+++ b/workflow-templates/first-merged-pr-comment.yml
@@ -38,11 +38,6 @@ jobs:
     permissions:
       pull-requests: write
 
-    env:
-      FIRST_MERGED_PR_MESSAGE: >-
-        ${{ vars.FIRST_MERGED_PR_MESSAGE ||
-        'Thanks {contributor_mention}! Your first pull request to {repository_name} has been merged.' }}
-
     steps:
       # pull_request_target is intentionally used without checkout. Nothing
       # from the pull request head is downloaded or executed.
@@ -52,4 +47,4 @@ jobs:
           github-token: ${{ github.token }}
           pull-request-number: >-
             ${{ github.event.pull_request.number || inputs.pull_request_number }}
-          message-template: ${{ env.FIRST_MERGED_PR_MESSAGE }}
+          message-template: ${{ vars.FIRST_MERGED_PR_MESSAGE }}