diff --git a/lang_agent/base.py b/lang_agent/base.py
index 479744a..21d99cd 100644
--- a/lang_agent/base.py
+++ b/lang_agent/base.py
@@ -31,4 +31,10 @@ class GraphBase(ABC):
         logger.info("creating image")
         img = Image.open(BytesIO(self.workflow.get_graph().draw_mermaid_png()))
         plt.imshow(img)
-        plt.show()
\ No newline at end of file
+        plt.show()
+
+
+class ToolNodeBase(GraphBase):
+    @abstractmethod
+    def get_streamable_tags(self)->List[List[str]]:
+        return [["tool_llm"]]
\ No newline at end of file