diff --git a/services/llm.ts b/services/llm.ts
index 80c439a..23b3f64 100644
--- a/services/llm.ts
+++ b/services/llm.ts
@@ -115,6 +115,7 @@ You are a professional podcaster. Create a detailed podcast script based on the
 - The podcast name must be "自動生成ポッドキャスト"
 
 **Format Requirements:**
+- Length: 1000-5000 characters (Japanese)
 - Use natural, conversational Japanese language suitable for audio
 - Write in a engaging podcast style with smooth transitions between topics
 - There is only **one speaker** in the podcast, so use first-person perspective