diff --git a/src/google/adk/tools/_function_parameter_parse_util.py b/src/google/adk/tools/_function_parameter_parse_util.py
index e61b61db56..848e181c1e 100644
--- a/src/google/adk/tools/_function_parameter_parse_util.py
+++ b/src/google/adk/tools/_function_parameter_parse_util.py
@@ -203,6 +203,22 @@ def _is_default_value_compatible(
           for item in default_value
       )
 
+    if origin is tuple:
+      if not isinstance(default_value, tuple):
+        return False
+      args = get_args(annotation)
+      if len(args) == 2 and args[1] is Ellipsis:
+        return all(
+            _is_default_value_compatible(item, args[0])
+            for item in default_value
+        )
+      if len(args) != len(default_value):
+        return False
+      return all(
+          _is_default_value_compatible(item, arg)
+          for item, arg in zip(default_value, args)
+      )
+
     if origin is Literal:
       return default_value in get_args(annotation)
 
@@ -334,6 +350,31 @@ def _parse_schema_from_parameter(
         schema.default = param.default
       _raise_if_schema_unsupported(variant, schema)
       return schema
+    if origin is tuple:
+      if len(args) == 2 and args[1] is Ellipsis:
+        item_annotation = args[0]
+      elif args and all(arg == args[0] for arg in args):
+        item_annotation = args[0]
+      else:
+        raise ValueError(
+            f'Tuple type {param.annotation} must use one repeated item type.'
+        )
+      schema.type = types.Type.ARRAY
+      schema.items = _parse_schema_from_parameter(
+          variant,
+          inspect.Parameter(
+              'item',
+              inspect.Parameter.POSITIONAL_OR_KEYWORD,
+              annotation=item_annotation,
+          ),
+          func_name,
+      )
+      if param.default is not inspect.Parameter.empty:
+        if not _is_default_value_compatible(param.default, param.annotation):
+          raise ValueError(default_value_error_msg)
+        schema.default = param.default
+      _raise_if_schema_unsupported(variant, schema)
+      return schema
     if origin in (Union, typing_types.UnionType):
       schema.any_of = []
       schema.type = types.Type.OBJECT
diff --git a/tests/unittests/tools/test_from_function_with_options.py b/tests/unittests/tools/test_from_function_with_options.py
index 4f77bc7b1f..839c431beb 100644
--- a/tests/unittests/tools/test_from_function_with_options.py
+++ b/tests/unittests/tools/test_from_function_with_options.py
@@ -228,6 +228,31 @@ def test_function(
   assert declaration.response.type == types.Type.STRING
 
 
+def test_from_function_with_tuple_type_parameter():
+  """Test from_function_with_options with tuple type parameter."""
+
+  def test_function(
+      coordinate: tuple[float, float],
+  ) -> str:
+    """Formats a coordinate pair."""
+    return f'{coordinate[0]}, {coordinate[1]}'
+
+  declaration = _automatic_function_calling_util.from_function_with_options(
+      test_function, GoogleLLMVariant.VERTEX_AI
+  )
+
+  assert declaration.name == 'test_function'
+  assert declaration.parameters.type == types.Type.OBJECT
+  assert declaration.parameters.properties['coordinate'].type == (
+      types.Type.ARRAY
+  )
+  assert (
+      declaration.parameters.properties['coordinate'].items.type
+      == types.Type.NUMBER
+  )
+  assert declaration.response.type == types.Type.STRING
+
+
 def test_from_function_with_collections_return_type():
   """Test from_function_with_options with collections return type."""
 
@@ -321,14 +346,8 @@ async def test_function(param: str) -> AsyncGenerator[Dict[str, str], None]:
   assert declaration.response.type == types.Type.OBJECT
 
 
-def test_required_fields_set_in_json_schema_fallback():
-  """Test that required fields are populated when the json_schema fallback path is used.
-
-  When a parameter has a complex type (e.g. tuple[str, ...] | None) that
-  _parse_schema_from_parameter can't handle, from_function_with_options falls
-  back to the parameters_json_schema branch. This test verifies that the
-  required fields are correctly populated in that fallback branch.
-  """
+def test_required_fields_set_with_optional_tuple_parameter():
+  """Test that required fields are populated with optional tuple parameters."""
 
   def complex_tool(
       query: str,
@@ -350,14 +369,9 @@ def complex_tool(
           'query': types.Schema(type=types.Type.STRING),
           'mode': types.Schema(type=types.Type.STRING, default='default'),
           'tags': types.Schema(
-              any_of=[
-                  types.Schema(
-                      items=types.Schema(type=types.Type.STRING),
-                      type=types.Type.ARRAY,
-                  ),
-                  types.Schema(type=types.Type.NULL),
-              ],
+              items=types.Schema(type=types.Type.STRING),
               nullable=True,
+              type=types.Type.ARRAY,
           ),
       },
   )