diff --git a/libs/core/langchain_core/tools/base.py b/libs/core/langchain_core/tools/base.py
index 5dcea96b17..a1cd5502f1 100644
--- a/libs/core/langchain_core/tools/base.py
+++ b/libs/core/langchain_core/tools/base.py
@@ -701,6 +701,17 @@ class ChildTool(BaseTool):
 
         full_schema = self.get_input_schema()
         fields = []
+
+        # Accommodates a condition where forward references were not resolved
+        # during model construction. At introspection time, we fail fast if
+        # the model schema is not complete so the underlying serialized schema
+        # doesn't narrow the propreties in the tool json schema to an empty dict
+        if (
+            is_pydantic_v2_subclass(full_schema)
+            and not full_schema.__pydantic_complete__
+        ):
+            full_schema.model_rebuild()
+
         for name, type_ in get_all_basemodel_annotations(full_schema).items():
             if not _is_injected_arg_type(type_):
                 fields.append(name)
diff --git a/libs/core/langchain_core/utils/pydantic.py b/libs/core/langchain_core/utils/pydantic.py
index ed6b3027cb..48de9c1305 100644
--- a/libs/core/langchain_core/utils/pydantic.py
+++ b/libs/core/langchain_core/utils/pydantic.py
@@ -11,6 +11,7 @@ from types import GenericAlias
 from typing import (
     TYPE_CHECKING,
     Any,
+    TypeGuard,
     TypeVar,
     cast,
     overload,
@@ -84,7 +85,7 @@ def is_pydantic_v1_subclass(cls: type) -> bool:
     return issubclass(cls, BaseModelV1)
 
 
-def is_pydantic_v2_subclass(cls: type) -> bool:
+def is_pydantic_v2_subclass(cls: type) -> TypeGuard[type[BaseModel]]:
     """Check if the given class is Pydantic v2-like.
 
     Returns:
diff --git a/libs/core/tests/unit_tests/test_tools.py b/libs/core/tests/unit_tests/test_tools.py
index d304b51fa2..9b16fa8b5f 100644
--- a/libs/core/tests/unit_tests/test_tools.py
+++ b/libs/core/tests/unit_tests/test_tools.py
@@ -31,6 +31,7 @@ from pydantic import (
     RootModel,
     ValidationError,
 )
+from pydantic.errors import PydanticUndefinedAnnotation
 from pydantic.v1 import BaseModel as BaseModelV1
 from pydantic.v1 import ValidationError as ValidationErrorV1
 from typing_extensions import TypedDict, override
@@ -3191,6 +3192,24 @@ def test_tool_decorator_description() -> None:
     )
 
 
+def test_inferred_args_schema_raises_for_unresolved_nested_forward_ref() -> None:
+    """Tool schemas should not silently drop incomplete Pydantic model fields."""
+
+    class Container(BaseModel):
+        # Intentionally unresolved; schema conversion must fail loudly.
+        rows: list["UndefinedRow"] = Field(  # type: ignore[name-defined]  # noqa: F821
+            default_factory=list
+        )
+
+    @tool
+    def my_tool(real_arg: str, container: Container) -> str:
+        """Process a container."""
+        return "ok"
+
+    with pytest.raises(PydanticUndefinedAnnotation, match="UndefinedRow"):
+        convert_to_openai_tool(my_tool)
+
+
 def test_title_property_preserved() -> None:
     """Test that the title property is preserved when generating schema.