diff --git a/libs/core/langchain_core/tools/base.py b/libs/core/langchain_core/tools/base.py
index daee8604307..52123ec6b4f 100644
--- a/libs/core/langchain_core/tools/base.py
+++ b/libs/core/langchain_core/tools/base.py
@@ -1077,16 +1077,18 @@ def get_all_basemodel_annotations(
     """
     # cls has no subscript: cls = FooBar
     if isinstance(cls, type):
+        # Gather pydantic field objects (v2: model_fields / v1: __fields__)
+        fields = getattr(cls, "model_fields", {}) or getattr(cls, "__fields__", {})
+        alias_map = {field.alias: name for name, field in fields.items() if field.alias}
+
         annotations: dict[str, type] = {}
         for name, param in inspect.signature(cls).parameters.items():
             # Exclude hidden init args added by pydantic Config. For example if
             # BaseModel(extra="allow") then "extra_data" will part of init sig.
-            if (
-                fields := getattr(cls, "model_fields", {})  # pydantic v2+
-                or getattr(cls, "__fields__", {})  # pydantic v1
-            ) and name not in fields:
+            if fields and name not in fields and name not in alias_map:
                 continue
-            annotations[name] = param.annotation
+            field_name = alias_map.get(name, name)
+            annotations[field_name] = param.annotation
         orig_bases: tuple = getattr(cls, "__orig_bases__", ())
     # cls has subscript: cls = FooBar[int]
     else:
diff --git a/libs/core/tests/unit_tests/test_tools.py b/libs/core/tests/unit_tests/test_tools.py
index 3ffc15ad0fd..025be61b461 100644
--- a/libs/core/tests/unit_tests/test_tools.py
+++ b/libs/core/tests/unit_tests/test_tools.py
@@ -2146,6 +2146,15 @@ def test__get_all_basemodel_annotations_v1() -> None:
     assert actual == expected
 
 
+def test_get_all_basemodel_annotations_aliases() -> None:
+    class CalculatorInput(BaseModel):
+        a: int = Field(description="first number", alias="A")
+        b: int = Field(description="second number")
+
+    actual = get_all_basemodel_annotations(CalculatorInput)
+    assert actual == {"a": int, "b": int}
+
+
 def test_tool_annotations_preserved() -> None:
     """Test that annotations are preserved when creating a tool."""