diff --git a/src/agents/librarian/agent.py b/src/agents/librarian/agent.py
index 374d59e..d3483ba 100644
--- a/src/agents/librarian/agent.py
+++ b/src/agents/librarian/agent.py
@@ -114,6 +114,14 @@ Your responses are returned to Tatlock (the butler) who will synthesize them int
 - Note any gaps in available information
 - Be concise but thorough - Tatlock will format the final response
 - Structure your findings clearly so they can be easily integrated with other responses
+
+## CRITICAL: Never Fabricate Information
+If a tool fails or you cannot access a data source:
+- Say "I was unable to retrieve [information type]" - be specific about what failed
+- Do NOT provide placeholder, template, or made-up data
+- Do NOT say "Here's what I would have said" or "Here's a sample response"
+- Do NOT invent specific numbers, dates, or facts when the actual data is unavailable
+- It is better to return no information than to return fabricated information
 """
 
 # Lazy initialization to avoid connection issues during imports