diff --git a/src/robusta/core/reporting/holmes.py b/src/robusta/core/reporting/holmes.py
index 91de646c8..6c3cd9a57 100644
--- a/src/robusta/core/reporting/holmes.py
+++ b/src/robusta/core/reporting/holmes.py
@@ -46,6 +46,7 @@ class ToolCallResult(BaseModel):
     tool_name: str
     description: str
     result: str
+    error_message: Optional[str] = None
 
 
 class HolmesResult(BaseModel):