diff --git a/src/google/adk/tools/openapi_tool/openapi_spec_parser/openapi_toolset.py b/src/google/adk/tools/openapi_tool/openapi_spec_parser/openapi_toolset.py
index fde0b37..1bfeac1 100644
--- a/src/google/adk/tools/openapi_tool/openapi_spec_parser/openapi_toolset.py
+++ b/src/google/adk/tools/openapi_tool/openapi_spec_parser/openapi_toolset.py
@@ -105,7 +105,7 @@ class OpenAPIToolset(BaseToolset):
     """
     if not spec_dict:
       spec_dict = self._load_spec(spec_str, spec_str_type)
-    self.tools: Final[List[RestApiTool]] = list(self._parse(spec_dict))
+    self._tools: Final[List[RestApiTool]] = list(self._parse(spec_dict))
     if auth_scheme or auth_credential:
       self._configure_auth_all(auth_scheme, auth_credential)
     self.tool_filter = tool_filter
@@ -115,7 +115,7 @@ class OpenAPIToolset(BaseToolset):
   ):
     """Configure auth scheme and credential for all tools."""
 
-    for tool in self.tools:
+    for tool in self._tools:
       if auth_scheme:
         tool.configure_auth_scheme(auth_scheme)
       if auth_credential:
@@ -128,7 +128,7 @@ class OpenAPIToolset(BaseToolset):
     """Get all tools in the toolset."""
     return [
         tool
-        for tool in self.tools
+        for tool in self._tools
         if self.tool_filter is None
         or (
             self.tool_filter(tool, readonly_context)
@@ -139,7 +139,7 @@ class OpenAPIToolset(BaseToolset):
 
   def get_tool(self, tool_name: str) -> Optional[RestApiTool]:
     """Get a tool by name."""
-    matching_tool = filter(lambda t: t.name == tool_name, self.tools)
+    matching_tool = filter(lambda t: t.name == tool_name, self._tools)
     return next(matching_tool, None)
 
   def _load_spec(
diff --git a/src/google/adk/tools/openapi_tool/openapi_spec_parser/operation_parser.py b/src/google/adk/tools/openapi_tool/openapi_spec_parser/operation_parser.py
index a7bed0f..84e8c4d 100644
--- a/src/google/adk/tools/openapi_tool/openapi_spec_parser/operation_parser.py
+++ b/src/google/adk/tools/openapi_tool/openapi_spec_parser/operation_parser.py
@@ -45,14 +45,14 @@ class OperationParser:
         should_parse: Whether to parse the operation during initialization.
     """
     if isinstance(operation, dict):
-      self.operation = Operation.model_validate(operation)
+      self._operation = Operation.model_validate(operation)
     elif isinstance(operation, str):
-      self.operation = Operation.model_validate_json(operation)
+      self._operation = Operation.model_validate_json(operation)
     else:
-      self.operation = operation
+      self._operation = operation
 
-    self.params: List[ApiParameter] = []
-    self.return_value: Optional[ApiParameter] = None
+    self._params: List[ApiParameter] = []
+    self._return_value: Optional[ApiParameter] = None
     if should_parse:
       self._process_operation_parameters()
       self._process_request_body()
@@ -67,13 +67,13 @@ class OperationParser:
       return_value: Optional[ApiParameter] = None,
   ) -> 'OperationParser':
     parser = cls(operation, should_parse=False)
-    parser.params = params
-    parser.return_value = return_value
+    parser._params = params
+    parser._return_value = return_value
     return parser
 
   def _process_operation_parameters(self):
     """Processes parameters from the OpenAPI operation."""
-    parameters = self.operation.parameters or []
+    parameters = self._operation.parameters or []
     for param in parameters:
       if isinstance(param, Parameter):
         original_name = param.name
@@ -86,7 +86,7 @@ class OperationParser:
         # param.required can be None
         required = param.required if param.required is not None else False
 
-        self.params.append(
+        self._params.append(
             ApiParameter(
                 original_name=original_name,
                 param_location=location,
@@ -98,7 +98,7 @@ class OperationParser:
 
   def _process_request_body(self):
     """Processes the request body from the OpenAPI operation."""
-    request_body = self.operation.requestBody
+    request_body = self._operation.requestBody
     if not request_body:
       return
 
@@ -114,7 +114,7 @@ class OperationParser:
       if schema and schema.type == 'object':
         properties = schema.properties or {}
         for prop_name, prop_details in properties.items():
-          self.params.append(
+          self._params.append(
               ApiParameter(
                   original_name=prop_name,
                   param_location='body',
@@ -124,7 +124,7 @@ class OperationParser:
           )
 
       elif schema and schema.type == 'array':
-        self.params.append(
+        self._params.append(
             ApiParameter(
                 original_name='array',
                 param_location='body',
@@ -133,7 +133,7 @@ class OperationParser:
             )
         )
       else:
-        self.params.append(
+        self._params.append(
             # Empty name for unnamed body param
             ApiParameter(
                 original_name='',
@@ -147,7 +147,7 @@ class OperationParser:
   def _dedupe_param_names(self):
     """Deduplicates parameter names to avoid conflicts."""
     params_cnt = {}
-    for param in self.params:
+    for param in self._params:
       name = param.py_name
       if name not in params_cnt:
         params_cnt[name] = 0
@@ -157,7 +157,7 @@ class OperationParser:
 
   def _process_return_value(self) -> Parameter:
     """Returns a Parameter object representing the return type."""
-    responses = self.operation.responses or {}
+    responses = self._operation.responses or {}
     # Default to Any if no 2xx response or if schema is missing
     return_schema = Schema(type='Any')
 
@@ -174,7 +174,7 @@ class OperationParser:
           return_schema = content[mime_type].schema_
           break
 
-    self.return_value = ApiParameter(
+    self._return_value = ApiParameter(
         original_name='',
         param_location='',
         param_schema=return_schema,
@@ -182,42 +182,42 @@ class OperationParser:
 
   def get_function_name(self) -> str:
     """Returns the generated function name."""
-    operation_id = self.operation.operationId
+    operation_id = self._operation.operationId
     if not operation_id:
       raise ValueError('Operation ID is missing')
     return to_snake_case(operation_id)[:60]
 
   def get_return_type_hint(self) -> str:
     """Returns the return type hint string (like 'str', 'int', etc.)."""
-    return self.return_value.type_hint
+    return self._return_value.type_hint
 
   def get_return_type_value(self) -> Any:
     """Returns the return type value (like str, int, List[str], etc.)."""
-    return self.return_value.type_value
+    return self._return_value.type_value
 
   def get_parameters(self) -> List[ApiParameter]:
     """Returns the list of Parameter objects."""
-    return self.params
+    return self._params
 
   def get_return_value(self) -> ApiParameter:
     """Returns the list of Parameter objects."""
-    return self.return_value
+    return self._return_value
 
   def get_auth_scheme_name(self) -> str:
     """Returns the name of the auth scheme for this operation from the spec."""
-    if self.operation.security:
-      scheme_name = list(self.operation.security[0].keys())[0]
+    if self._operation.security:
+      scheme_name = list(self._operation.security[0].keys())[0]
       return scheme_name
     return ''
 
   def get_pydoc_string(self) -> str:
     """Returns the generated PyDoc string."""
-    pydoc_params = [param.to_pydoc_string() for param in self.params]
+    pydoc_params = [param.to_pydoc_string() for param in self._params]
     pydoc_description = (
-        self.operation.summary or self.operation.description or ''
+        self._operation.summary or self._operation.description or ''
     )
     pydoc_return = PydocHelper.generate_return_doc(
-        self.operation.responses or {}
+        self._operation.responses or {}
     )
     pydoc_arg_list = chr(10).join(
         f'        {param_doc}' for param_doc in pydoc_params
@@ -236,12 +236,12 @@ class OperationParser:
     """Returns the JSON schema for the function arguments."""
     properties = {
         p.py_name: jsonable_encoder(p.param_schema, exclude_none=True)
-        for p in self.params
+        for p in self._params
     }
     return {
         'properties': properties,
-        'required': [p.py_name for p in self.params if p.required],
-        'title': f"{self.operation.operationId or 'unnamed'}_Arguments",
+        'required': [p.py_name for p in self._params if p.required],
+        'title': f"{self._operation.operationId or 'unnamed'}_Arguments",
         'type': 'object',
     }
 
@@ -253,11 +253,11 @@ class OperationParser:
             inspect.Parameter.POSITIONAL_OR_KEYWORD,
             annotation=param.type_value,
         )
-        for param in self.params
+        for param in self._params
     ]
 
   def get_annotations(self) -> Dict[str, Any]:
     """Returns a dictionary of parameter annotations for the function."""
-    annotations = {p.py_name: p.type_value for p in self.params}
+    annotations = {p.py_name: p.type_value for p in self._params}
     annotations['return'] = self.get_return_type_value()
     return annotations
diff --git a/tests/unittests/tools/openapi_tool/openapi_spec_parser/test_openapi_toolset.py b/tests/unittests/tools/openapi_tool/openapi_spec_parser/test_openapi_toolset.py
index 1b1e218..fdb6d20 100644
--- a/tests/unittests/tools/openapi_tool/openapi_spec_parser/test_openapi_toolset.py
+++ b/tests/unittests/tools/openapi_tool/openapi_spec_parser/test_openapi_toolset.py
@@ -47,18 +47,18 @@ def openapi_spec() -> Dict:
 def test_openapi_toolset_initialization_from_dict(openapi_spec: Dict):
   """Test initialization of OpenAPIToolset with a dictionary."""
   toolset = OpenAPIToolset(spec_dict=openapi_spec)
-  assert isinstance(toolset.tools, list)
-  assert len(toolset.tools) == 5
-  assert all(isinstance(tool, RestApiTool) for tool in toolset.tools)
+  assert isinstance(toolset._tools, list)
+  assert len(toolset._tools) == 5
+  assert all(isinstance(tool, RestApiTool) for tool in toolset._tools)
 
 
 def test_openapi_toolset_initialization_from_yaml_string(openapi_spec: Dict):
   """Test initialization of OpenAPIToolset with a YAML string."""
   spec_str = yaml.dump(openapi_spec)
   toolset = OpenAPIToolset(spec_str=spec_str, spec_str_type="yaml")
-  assert isinstance(toolset.tools, list)
-  assert len(toolset.tools) == 5
-  assert all(isinstance(tool, RestApiTool) for tool in toolset.tools)
+  assert isinstance(toolset._tools, list)
+  assert len(toolset._tools) == 5
+  assert all(isinstance(tool, RestApiTool) for tool in toolset._tools)
 
 
 def test_openapi_toolset_tool_existing(openapi_spec: Dict):
@@ -134,6 +134,6 @@ def test_openapi_toolset_configure_auth_on_init(openapi_spec: Dict):
       auth_scheme=auth_scheme,
       auth_credential=auth_credential,
   )
-  for tool in toolset.tools:
+  for tool in toolset._tools:
     assert tool.auth_scheme == auth_scheme
     assert tool.auth_credential == auth_credential
diff --git a/tests/unittests/tools/openapi_tool/openapi_spec_parser/test_operation_parser.py b/tests/unittests/tools/openapi_tool/openapi_spec_parser/test_operation_parser.py
index 653590e..26cb944 100644
--- a/tests/unittests/tools/openapi_tool/openapi_spec_parser/test_operation_parser.py
+++ b/tests/unittests/tools/openapi_tool/openapi_spec_parser/test_operation_parser.py
@@ -78,31 +78,31 @@ def sample_operation() -> Operation:
 def test_operation_parser_initialization(sample_operation):
   """Test initialization of OperationParser."""
   parser = OperationParser(sample_operation)
-  assert parser.operation == sample_operation
-  assert len(parser.params) == 4  # 2 params + 2 request body props
-  assert parser.return_value is not None
+  assert parser._operation == sample_operation
+  assert len(parser._params) == 4  # 2 params + 2 request body props
+  assert parser._return_value is not None
 
 
 def test_process_operation_parameters(sample_operation):
   """Test _process_operation_parameters method."""
   parser = OperationParser(sample_operation, should_parse=False)
   parser._process_operation_parameters()
-  assert len(parser.params) == 2
-  assert parser.params[0].original_name == 'param1'
-  assert parser.params[0].param_location == 'query'
-  assert parser.params[1].original_name == 'param2'
-  assert parser.params[1].param_location == 'header'
+  assert len(parser._params) == 2
+  assert parser._params[0].original_name == 'param1'
+  assert parser._params[0].param_location == 'query'
+  assert parser._params[1].original_name == 'param2'
+  assert parser._params[1].param_location == 'header'
 
 
 def test_process_request_body(sample_operation):
   """Test _process_request_body method."""
   parser = OperationParser(sample_operation, should_parse=False)
   parser._process_request_body()
-  assert len(parser.params) == 2  # 2 properties in request body
-  assert parser.params[0].original_name == 'prop1'
-  assert parser.params[0].param_location == 'body'
-  assert parser.params[1].original_name == 'prop2'
-  assert parser.params[1].param_location == 'body'
+  assert len(parser._params) == 2  # 2 properties in request body
+  assert parser._params[0].original_name == 'prop1'
+  assert parser._params[0].param_location == 'body'
+  assert parser._params[1].original_name == 'prop2'
+  assert parser._params[1].param_location == 'body'
 
 
 def test_process_request_body_array():
@@ -132,20 +132,20 @@ def test_process_request_body_array():
 
   parser = OperationParser(operation, should_parse=False)
   parser._process_request_body()
-  assert len(parser.params) == 1
-  assert parser.params[0].original_name == 'array'
-  assert parser.params[0].param_location == 'body'
+  assert len(parser._params) == 1
+  assert parser._params[0].original_name == 'array'
+  assert parser._params[0].param_location == 'body'
   # Check that schema is correctly propagated and is a dictionary
-  assert parser.params[0].param_schema.type == 'array'
-  assert parser.params[0].param_schema.items.type == 'object'
-  assert 'item_prop1' in parser.params[0].param_schema.items.properties
-  assert 'item_prop2' in parser.params[0].param_schema.items.properties
+  assert parser._params[0].param_schema.type == 'array'
+  assert parser._params[0].param_schema.items.type == 'object'
+  assert 'item_prop1' in parser._params[0].param_schema.items.properties
+  assert 'item_prop2' in parser._params[0].param_schema.items.properties
   assert (
-      parser.params[0].param_schema.items.properties['item_prop1'].description
+      parser._params[0].param_schema.items.properties['item_prop1'].description
       == 'Item Property 1'
   )
   assert (
-      parser.params[0].param_schema.items.properties['item_prop2'].description
+      parser._params[0].param_schema.items.properties['item_prop2'].description
       == 'Item Property 2'
   )
 
@@ -159,9 +159,9 @@ def test_process_request_body_no_name():
   )
   parser = OperationParser(operation, should_parse=False)
   parser._process_request_body()
-  assert len(parser.params) == 1
-  assert parser.params[0].original_name == ''  # No name
-  assert parser.params[0].param_location == 'body'
+  assert len(parser._params) == 1
+  assert parser._params[0].original_name == ''  # No name
+  assert parser._params[0].param_location == 'body'
 
 
 def test_process_request_body_empty_object():
@@ -173,30 +173,30 @@ def test_process_request_body_empty_object():
   )
   parser = OperationParser(operation, should_parse=False)
   parser._process_request_body()
-  assert len(parser.params) == 0
+  assert len(parser._params) == 0
 
 
 def test_dedupe_param_names(sample_operation):
   """Test _dedupe_param_names method."""
   parser = OperationParser(sample_operation, should_parse=False)
   # Add duplicate named parameters.
-  parser.params = [
+  parser._params = [
       ApiParameter(original_name='test', param_location='', param_schema={}),
       ApiParameter(original_name='test', param_location='', param_schema={}),
       ApiParameter(original_name='test', param_location='', param_schema={}),
   ]
   parser._dedupe_param_names()
-  assert parser.params[0].py_name == 'test'
-  assert parser.params[1].py_name == 'test_0'
-  assert parser.params[2].py_name == 'test_1'
+  assert parser._params[0].py_name == 'test'
+  assert parser._params[1].py_name == 'test_0'
+  assert parser._params[2].py_name == 'test_1'
 
 
 def test_process_return_value(sample_operation):
   """Test _process_return_value method."""
   parser = OperationParser(sample_operation, should_parse=False)
   parser._process_return_value()
-  assert parser.return_value is not None
-  assert parser.return_value.type_hint == 'str'
+  assert parser._return_value is not None
+  assert parser._return_value.type_hint == 'str'
 
 
 def test_process_return_value_no_2xx(sample_operation):
@@ -206,8 +206,8 @@ def test_process_return_value_no_2xx(sample_operation):
   )
   parser = OperationParser(operation_no_2xx, should_parse=False)
   parser._process_return_value()
-  assert parser.return_value is not None
-  assert parser.return_value.type_hint == 'Any'
+  assert parser._return_value is not None
+  assert parser._return_value.type_hint == 'Any'
 
 
 def test_process_return_value_multiple_2xx(sample_operation):
@@ -242,10 +242,10 @@ def test_process_return_value_multiple_2xx(sample_operation):
   parser = OperationParser(operation_multi_2xx, should_parse=False)
   parser._process_return_value()
 
-  assert parser.return_value is not None
+  assert parser._return_value is not None
   # Take the content type of the 200 response since it's the smallest response
   # code
-  assert parser.return_value.param_schema.type == 'boolean'
+  assert parser._return_value.param_schema.type == 'boolean'
 
 
 def test_process_return_value_no_content(sample_operation):
@@ -255,7 +255,7 @@ def test_process_return_value_no_content(sample_operation):
   )
   parser = OperationParser(operation_no_content, should_parse=False)
   parser._process_return_value()
-  assert parser.return_value.type_hint == 'Any'
+  assert parser._return_value.type_hint == 'Any'
 
 
 def test_process_return_value_no_schema(sample_operation):
@@ -270,7 +270,7 @@ def test_process_return_value_no_schema(sample_operation):
   )
   parser = OperationParser(operation_no_schema, should_parse=False)
   parser._process_return_value()
-  assert parser.return_value.type_hint == 'Any'
+  assert parser._return_value.type_hint == 'Any'
 
 
 def test_get_function_name(sample_operation):
@@ -389,9 +389,9 @@ def test_load():
   parser = OperationParser.load(operation, params, return_value)
 
   assert isinstance(parser, OperationParser)
-  assert parser.operation == operation
-  assert parser.params == params
-  assert parser.return_value == return_value
+  assert parser._operation == operation
+  assert parser._params == params
+  assert parser._return_value == return_value
   assert (
       parser.get_function_name() == 'my_op'
   )  # Check that the operation is loaded
@@ -412,7 +412,7 @@ def test_operation_parser_with_dict():
       },
   }
   parser = OperationParser(operation_dict)
-  assert parser.operation.operationId == 'test_dict_operation'
-  assert len(parser.params) == 1
-  assert parser.params[0].original_name == 'dict_param'
-  assert parser.return_value.type_hint == 'str'
+  assert parser._operation.operationId == 'test_dict_operation'
+  assert len(parser._params) == 1
+  assert parser._params[0].original_name == 'dict_param'
+  assert parser._return_value.type_hint == 'str'