fix(core): fix support of Pydantic v1 models in BaseTool.args (#32487)

Co-authored-by: Eugene Yurtsev <eyurtsev@gmail.com>

libs/core/langchain_core/tools/base.py

@@ -546,6 +546,8 @@ class ChildTool(BaseTool):
         """
         if isinstance(self.args_schema, dict):
             json_schema = self.args_schema
+        elif self.args_schema and issubclass(self.args_schema, BaseModelV1):
+            json_schema = self.args_schema.schema()
         else:
             input_schema = self.get_input_schema()
             json_schema = input_schema.model_json_schema()

libs/core/langchain_core/tools/simple.py

@@ -64,11 +64,7 @@ class Tool(BaseTool):
             The input arguments for the tool.
         """
         if self.args_schema is not None:
-            if isinstance(self.args_schema, dict):
-                json_schema = self.args_schema
-            else:
-                json_schema = self.args_schema.model_json_schema()
-            return json_schema["properties"]
+            return super().args
         # For backwards compatibility, if the function signature is ambiguous,
         # assume it takes a single string input.
         return {"tool_input": {"type": "string"}}

libs/core/langchain_core/tools/structured.py

@@ -67,16 +67,6 @@ class StructuredTool(BaseTool):
 
     # --- Tool ---
 
-    @property
-    def args(self) -> dict:
-        """The tool's input arguments."""
-        if isinstance(self.args_schema, dict):
-            json_schema = self.args_schema
-        else:
-            input_schema = self.get_input_schema()
-            json_schema = input_schema.model_json_schema()
-        return json_schema["properties"]
-
     def _run(
         self,
         *args: Any,

libs/core/tests/unit_tests/test_tools.py

@@ -1904,6 +1904,11 @@ def test_args_schema_as_pydantic(pydantic_model: Any) -> None:
         name="some_tool", description="some description", args_schema=pydantic_model
     )
 
+    assert tool.args == {
+        "a": {"title": "A", "type": "integer"},
+        "b": {"title": "B", "type": "string"},
+    }
+
     input_schema = tool.get_input_schema()
     if issubclass(input_schema, BaseModel):
         input_json_schema = input_schema.model_json_schema()