Preserve Google Agent Identity token-sharing policy when constructing MCP tools

src/google/adk/tools/mcp_tool/mcp_tool.py

@@ -18,7 +18,6 @@
 import base64
 import inspect
 import logging
-import os
 from typing import Any
 from typing import Callable
 from typing import Dict
@@ -179,15 +178,6 @@ def __init__(
         ValueError: If mcp_tool or mcp_session_manager is None.
     """
 
-    # --- BEGIN BOUND TOKEN PATCH ---
-    # Set GOOGLE_API_PREVENT_AGENT_TOKEN_SHARING_FOR_GCP_SERVICES to false
-    # to disable bound token sharing. Tracking on
-    # https://github.com/google/adk-python/issues/5361
-    os.environ["GOOGLE_API_PREVENT_AGENT_TOKEN_SHARING_FOR_GCP_SERVICES"] = (
-        "false"
-    )
-    # --- END BOUND TOKEN PATCH ---
-
     super().__init__(
         name=mcp_tool.name,
         description=mcp_tool.description if mcp_tool.description else "",

src/google/adk/tools/mcp_tool/mcp_toolset.py

@@ -17,7 +17,6 @@
 import asyncio
 import base64
 import logging
-import os
 import sys
 from typing import Any
 from typing import Awaitable
@@ -161,15 +160,6 @@ def __init__(
         in a credential service. Used with auth_scheme.
     """
 
-    # --- BEGIN BOUND TOKEN PATCH ---
-    # Set GOOGLE_API_PREVENT_AGENT_TOKEN_SHARING_FOR_GCP_SERVICES to false
-    # to disable bound token sharing. Tracking on
-    # https://github.com/google/adk-python/issues/5361
-    os.environ["GOOGLE_API_PREVENT_AGENT_TOKEN_SHARING_FOR_GCP_SERVICES"] = (
-        "false"
-    )
-    # --- END BOUND TOKEN  PATCH ---
-
     super().__init__(tool_filter=tool_filter, tool_name_prefix=tool_name_prefix)
 
     self._sampling_callback = sampling_callback

tests/unittests/tools/mcp_tool/test_mcp_tool.py

@@ -12,12 +12,13 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import inspect
+import os
 from unittest.mock import AsyncMock
 from unittest.mock import create_autospec
 from unittest.mock import Mock
 from unittest.mock import patch
 
+from google.auth import _agent_identity_utils
 from google.adk.agents.context import Context
 from google.adk.auth.auth_credential import AuthCredential
 from google.adk.auth.auth_credential import AuthCredentialTypes
@@ -32,7 +33,6 @@
 from google.adk.tools.mcp_tool.mcp_tool import MCPTool
 from google.adk.tools.tool_context import ToolContext
 from google.genai.types import FunctionDeclaration
-from google.genai.types import Type
 from mcp.types import CallToolResult
 from mcp.types import TextContent
 import pytest
@@ -204,6 +204,29 @@ def test_init_basic(self):
     assert tool._mcp_tool == self.mock_mcp_tool
     assert tool._mcp_session_manager == self.mock_session_manager
 
+  def test_init_preserves_agent_identity_bound_token_opt_in(
+      self, monkeypatch
+  ):
+    """MCPTool construction should not disable process-wide bound tokens."""
+    env_name = "GOOGLE_API_PREVENT_AGENT_TOKEN_SHARING_FOR_GCP_SERVICES"
+    fake_cert = object()
+    monkeypatch.setenv(env_name, "true")
+    monkeypatch.setattr(
+        _agent_identity_utils,
+        "_is_agent_identity_certificate",
+        lambda cert: True,
+    )
+
+    assert _agent_identity_utils.should_request_bound_token(fake_cert)
+
+    MCPTool(
+        mcp_tool=self.mock_mcp_tool,
+        mcp_session_manager=self.mock_session_manager,
+    )
+
+    assert os.environ[env_name] == "true"
+    assert _agent_identity_utils.should_request_bound_token(fake_cert)
+
   def test_init_with_auth(self):
     """Test initialization with authentication."""
     # Create real auth scheme instances instead of mocks

tests/unittests/tools/mcp_tool/test_mcp_toolset.py

@@ -14,14 +14,15 @@
 
 import asyncio
 import base64
-from io import StringIO
+import os
 import pickle
 import sys
 from unittest.mock import AsyncMock
 from unittest.mock import MagicMock
 from unittest.mock import Mock
 
 from fastapi.openapi.models import OAuth2
+from google.auth import _agent_identity_utils
 from google.adk.agents.readonly_context import ReadonlyContext
 from google.adk.auth.auth_credential import AuthCredential
 from google.adk.auth.auth_credential import AuthCredentialTypes
@@ -89,6 +90,26 @@ def test_init_basic(self):
     assert toolset._auth_credential is None
     assert toolset._use_mcp_resources is False
 
+  def test_init_preserves_agent_identity_bound_token_opt_in(
+      self, monkeypatch
+  ):
+    """McpToolset construction should not disable process-wide bound tokens."""
+    env_name = "GOOGLE_API_PREVENT_AGENT_TOKEN_SHARING_FOR_GCP_SERVICES"
+    fake_cert = object()
+    monkeypatch.setenv(env_name, "true")
+    monkeypatch.setattr(
+        _agent_identity_utils,
+        "_is_agent_identity_certificate",
+        lambda cert: True,
+    )
+
+    assert _agent_identity_utils.should_request_bound_token(fake_cert)
+
+    McpToolset(connection_params=self.mock_stdio_params)
+
+    assert os.environ[env_name] == "true"
+    assert _agent_identity_utils.should_request_bound_token(fake_cert)
+
   def test_init_with_use_mcp_resources(self):
     """Test initialization with use_mcp_resources."""
     toolset = McpToolset(