diff --git a/python/cocoindex/typing.py b/python/cocoindex/typing.py
index 2eacad9f..f640af43 100644
--- a/python/cocoindex/typing.py
+++ b/python/cocoindex/typing.py
@@ -1,6 +1,7 @@
 import typing
 import collections
 import dataclasses
+import types
 from typing import Annotated, NamedTuple, Any, TypeVar, TYPE_CHECKING
 
 class Vector(NamedTuple):
@@ -59,16 +60,31 @@ class AnalyzedTypeInfo:
     elem_type: type | None
     struct_fields: tuple[dataclasses.Field, ...] | None
     attrs: dict[str, Any] | None
+    nullable: bool = False
 
 def analyze_type_info(t) -> AnalyzedTypeInfo:
     """
     Analyze a Python type and return the analyzed info.
     """
     annotations: tuple[Annotation, ...] = ()
-    if typing.get_origin(t) is Annotated:
-        annotations = t.__metadata__
-        t = t.__origin__
-    base_type = typing.get_origin(t)
+    base_type = None
+    nullable = False
+    while True:
+        base_type = typing.get_origin(t)
+        if base_type is Annotated:
+            annotations = t.__metadata__
+            t = t.__origin__
+        elif base_type is types.UnionType:
+            possible_types = typing.get_args(t)
+            non_none_types = [arg for arg in possible_types if arg not in (None, types.NoneType)]
+            if len(non_none_types) != 1:
+                raise ValueError(
+                    f"Expect exactly one non-None choice for Union type, but got {len(non_none_types)}: {t}")
+            t = non_none_types[0]
+            if len(possible_types) > 1:
+                nullable = True
+        else:
+            break
 
     attrs = None
     vector_info = None
@@ -118,7 +134,7 @@ def analyze_type_info(t) -> AnalyzedTypeInfo:
             raise ValueError(f"type unsupported yet: {base_type}")
 
     return AnalyzedTypeInfo(kind=kind, vector_info=vector_info, elem_type=elem_type,
-                            struct_fields=struct_fields, attrs=attrs)
+                            struct_fields=struct_fields, attrs=attrs, nullable=nullable)
 
 def _encode_type(type_info: AnalyzedTypeInfo) -> dict[str, Any]:
     encoded_type: dict[str, Any] = { 'kind': type_info.kind }
@@ -150,9 +166,15 @@ def _encode_type(type_info: AnalyzedTypeInfo) -> dict[str, Any]:
 
 def _encode_enriched_type(t) -> dict[str, Any]:
     enriched_type_info = analyze_type_info(t)
-    encoded = {'type': _encode_type(enriched_type_info)}
+
+    encoded: dict[str, Any] = {'type': _encode_type(enriched_type_info)}
+
     if enriched_type_info.attrs is not None:
         encoded['attrs'] = enriched_type_info.attrs
+
+    if enriched_type_info.nullable:
+        encoded['nullable'] = True
+
     return encoded