q

libs/core/langchain_core/tools.py

@@ -333,7 +333,11 @@ class ChildTool(BaseTool):
             tool_input if isinstance(tool_input, str) else str(tool_input),
             color=start_color,
             name=run_name,
-            inputs=tool_input,
+            # Inputs by definition should always be dicts.
+            # For now, it's unclear whether this assumption is ever violated,
+            # but if it is we will send a `None` value to the callback instead
+            # And will need to address issue via a patch.
+            inputs=None if isinstance(tool_input, str) else tool_input,
             **kwargs,
         )
         try:
@@ -742,7 +746,7 @@ def tool(
     return_direct: bool = False,
     args_schema: Optional[Type[BaseModel]] = None,
     infer_schema: bool = True,
-) -> Callable[[Union[str, Callable, Runnable]], BaseTool]:
+) -> Callable:
     """Make tools out of functions, can be used with or without arguments.
 
     Args:
@@ -772,9 +776,7 @@ def tool(
                 return
     """
 
-    def _make_with_name(
-        tool_name: str
-    ) -> Callable[[Union[Callable, Runnable]], BaseTool]:
+    def _make_with_name(tool_name: str) -> Callable:
         def _make_tool(dec_func: Union[Callable, Runnable]) -> BaseTool:
             if isinstance(dec_func, Runnable):
                 runnable = dec_func

libs/core/langchain_core/tracers/langchain.py

@@ -112,7 +112,7 @@ class LangChainTracer(BaseTracer):
         metadata: Optional[Dict[str, Any]] = None,
         name: Optional[str] = None,
         **kwargs: Any,
-    ) -> None:
+    ) -> Any:
         """Start a trace for an LLM run."""
         parent_run_id_ = str(parent_run_id) if parent_run_id else None
         execution_order = self._get_execution_order(parent_run_id_)

libs/core/tests/unit_tests/runnables/test_runnable_events.py

@@ -17,7 +17,7 @@ from langchain_core.runnables import (
     RunnableLambda,
 )
 from langchain_core.runnables.utils import StreamEvent
-from langchain_core.tools import tool
+from langchain_core.tools import BaseTool, tool
 from tests.unit_tests.fake.chat_model import GenericFakeChatModel
 
 
@@ -942,5 +942,41 @@ async def test_event_stream_with_retry() -> None:
     ]
 
 
-def test_foo() -> None:
-    assert "Add tool test with single input (old style)" == 1
+async def test_with_inheritance_based_tool() -> None:
+    """Test with a tool created using inheritance."""
+
+    class CustomTool(BaseTool):
+        name = "is_cat_good_for_me"
+        description = "Find out what having a cat leads to!"
+
+        def _run(self, inputs: str) -> str:
+            return "success"
+
+    tool = CustomTool()
+    events = await _collect_events(tool.astream_events("q"))
+    assert events == [
+        {
+            "data": {"input": "q"},
+            "event": "on_tool_start",
+            "metadata": {},
+            "name": "is_cat_good_for_me",
+            "run_id": "",
+            "tags": [],
+        },
+        {
+            "data": {"chunk": "success"},
+            "event": "on_tool_stream",
+            "metadata": {},
+            "name": "is_cat_good_for_me",
+            "run_id": "",
+            "tags": [],
+        },
+        {
+            "data": {"output": "success"},
+            "event": "on_tool_end",
+            "metadata": {},
+            "name": "is_cat_good_for_me",
+            "run_id": "",
+            "tags": [],
+        },
+    ]