diff --git a/action.yml b/action.yml
index a80dfca..eddc2fc 100644
--- a/action.yml
+++ b/action.yml
@@ -26,6 +26,9 @@ branding:
 runs:
   using: 'composite'
   steps:
+    - run: |
+        [[ "${{ inputs.channel }}" ]] || { echo "required input 'channel' not specified" ; exit 1; }
+        [[ "${{ inputs.text }}" ]] || { echo "required input 'text' not specified" ; exit 1; }
     - shell: bash
       run: |
         response=$(curl --fail-with-body --silent --show-error \