diff --git a/model-serving/model_api/protocol.py b/model-serving/model_api/protocol.py
index 99f6eebd0..dcffdce40 100644
--- a/model-serving/model_api/protocol.py
+++ b/model-serving/model_api/protocol.py
@@ -93,7 +93,7 @@ class Type(Enum):
 class Tool(BaseModel):
     type: Type
     function: FunctionDef
-    id: str
+    id: str | None = None
 
 
 class SamplingParams(SamplingParams):