diff --git a/libs/core/langchain_core/tools/base.py b/libs/core/langchain_core/tools/base.py
index e54a09709d6..6d0baf148dd 100644
--- a/libs/core/langchain_core/tools/base.py
+++ b/libs/core/langchain_core/tools/base.py
@@ -687,9 +687,7 @@ class ChildTool(BaseTool):
                     f"args_schema must be a Pydantic BaseModel, got {self.args_schema}"
                 )
                 raise NotImplementedError(msg)
-            return {
-                k: getattr(result, k) for k, v in result_dict.items() if k in tool_input
-            }
+            return {k: getattr(result, k) for k, v in result_dict.items()}
         return tool_input
 
     @model_validator(mode="before")
diff --git a/libs/core/tests/unit_tests/test_tools.py b/libs/core/tests/unit_tests/test_tools.py
index 57b4573d70d..5278b641f75 100644
--- a/libs/core/tests/unit_tests/test_tools.py
+++ b/libs/core/tests/unit_tests/test_tools.py
@@ -21,7 +21,7 @@ from typing import (
 )
 
 import pytest
-from pydantic import BaseModel, Field, ValidationError
+from pydantic import BaseModel, Field, ValidationError, model_validator
 from pydantic.v1 import BaseModel as BaseModelV1
 from pydantic.v1 import ValidationError as ValidationErrorV1
 from typing_extensions import TypedDict
@@ -634,7 +634,7 @@ def test_named_tool_decorator_return_direct() -> None:
     """Test functionality when arguments and return direct are provided as input."""
 
     @tool("search", return_direct=True)
-    def search_api(query: str, *args: Any) -> str:
+    def search_api(query: str) -> str:
         """Search the API for the query."""
         return "API result"
 
@@ -2547,6 +2547,38 @@ def test_tool_decorator_description() -> None:
     )
 
 
+def test_tool_args_schema_with_pydantic_validator() -> None:
+    class NestedArgsSchema(BaseModel):
+        y: int
+
+    class ArgsSchema(BaseModel):
+        x: NestedArgsSchema
+
+        @model_validator(mode="before")
+        def wrap_in_x(cls, data: Any) -> Any:  # noqa: N805
+            if not isinstance(data, dict):
+                return {"x": data}
+
+            if "x" not in data:
+                return {"x": data}
+            return data
+
+    @tool(args_schema=ArgsSchema)
+    def foo(**args: Any) -> ArgsSchema:
+        """Bar."""
+        return ArgsSchema.model_validate(args)
+
+    # Test case where validator is identity function
+    valid_inputs = {"x": {"y": 5}}
+    assert foo.invoke(valid_inputs) == ArgsSchema.model_validate(valid_inputs)
+
+    # Test case where validator wraps input in "x"
+    invalid_inputs = {"y": 5}
+    assert foo.invoke(invalid_inputs) == ArgsSchema.model_validate(
+        {"x": invalid_inputs}
+    )
+
+
 def test_title_property_preserved() -> None:
     """Test that the title property is preserved when generating schema.