diff --git a/README.md b/README.md
index dd37a57..b8fa8e1 100644
--- a/README.md
+++ b/README.md
@@ -24,4 +24,10 @@ rake test
 
 # run a specific test
 ruby ./test/07_test.rb
+
+# scaffold a day
+rake scaffold:1
+
+# download test input
+rake download:1
 ```
diff --git a/Rakefile b/Rakefile
index 7e4345f..636b699 100644
--- a/Rakefile
+++ b/Rakefile
@@ -43,7 +43,10 @@ namespace :download do
 
   def download_input(number)
     session_path = File.join(APP_ROOT, '.session')
-    return '' unless File.exist?(session_path)
+
+    unless File.exist?(session_path)
+      raise 'Copy your session cookie from a logged-in browser and save it to a file at `.session`!'
+    end
 
     puts "⬇️ Download day #{number} input"