fix(api_registry): only attach ADC credentials to Google API hosts

ApiRegistry.get_toolset attaches the runtime's Application Default
Credentials to the MCP server URL from the API Registry listing without
checking the host, so the runtime's Google credentials can be sent to a
non-Google host registered in the catalog. AgentRegistry already gates
the same credentials behind a Google-host check (_is_google_api); this
brings ApiRegistry in line. Non-Google servers can authenticate via
header_provider.

Author: evilgensec

src/google/adk/integrations/api_registry/api_registry.py

@@ -16,6 +16,7 @@
 
 from typing import Any
 from typing import Callable
+from urllib.parse import urlparse
 
 from google.adk.agents.readonly_context import ReadonlyContext
 from google.adk.tools.base_toolset import ToolPredicate
@@ -28,6 +29,14 @@
 API_REGISTRY_URL = "https://cloudapiregistry.googleapis.com"
 
 
+def _is_google_api(url: str) -> bool:
+  """Returns True if the URL points to a Google API host."""
+  hostname = urlparse(url).hostname
+  return hostname is not None and (
+      hostname == "googleapis.com" or hostname.endswith(".googleapis.com")
+  )
+
+
 class ApiRegistry:
   """Registry that provides McpToolsets for MCP servers registered in API Registry."""
 
@@ -110,12 +119,19 @@ def get_toolset(
       raise ValueError(f"MCP server {mcp_server_name} has no URLs.")
 
     mcp_server_url = server["urls"][0]
-    headers = self._get_auth_headers()
 
     # Only prepend "https://" if the URL doesn't already have a scheme
     if not mcp_server_url.startswith(("http://", "https://")):
       mcp_server_url = "https://" + mcp_server_url
 
+    # Only attach the runtime's Application Default Credentials to Google API
+    # hosts. The server URL comes from the API Registry listing and may point at
+    # a non-Google host, which must not receive the runtime's Google
+    # credentials. This mirrors AgentRegistry, which gates the same credentials
+    # with _is_google_api. Non-Google servers can authenticate via
+    # header_provider.
+    headers = self._get_auth_headers() if _is_google_api(mcp_server_url) else {}
+
     return McpToolset(
         connection_params=StreamableHTTPConnectionParams(
             url=mcp_server_url,

tests/unittests/integrations/api_registry/test_api_registry.py

@@ -33,6 +33,10 @@
             "name": "test-mcp-server-2",
             "urls": ["mcp.server2.com"],
         },
+        {
+            "name": "test-mcp-server-google",
+            "urls": ["mcp.googleapis.com"],
+        },
         {
             "name": "test-mcp-server-no-url",
         },
@@ -79,7 +83,7 @@ def test_init_success(self, MockHttpClient):
         api_registry_project_id=self.project_id, location=self.location
     )
 
-    self.assertEqual(len(api_registry._mcp_servers), 5)
+    self.assertEqual(len(api_registry._mcp_servers), 6)
     self.assertIn("test-mcp-server-1", api_registry._mcp_servers)
     self.assertIn("test-mcp-server-2", api_registry._mcp_servers)
     self.assertIn("test-mcp-server-no-url", api_registry._mcp_servers)
@@ -107,7 +111,7 @@ def test_init_with_quota_project_id_success(self, MockHttpClient):
         api_registry_project_id=self.project_id, location=self.location
     )
 
-    self.assertEqual(len(api_registry._mcp_servers), 5)
+    self.assertEqual(len(api_registry._mcp_servers), 6)
     self.assertIn("test-mcp-server-1", api_registry._mcp_servers)
     self.assertIn("test-mcp-server-2", api_registry._mcp_servers)
     self.assertIn("test-mcp-server-no-url", api_registry._mcp_servers)
@@ -237,9 +241,43 @@ async def test_get_toolset_success(self, MockHttpClient, MockMcpToolset):
 
     toolset = api_registry.get_toolset("test-mcp-server-1")
 
+    # A non-Google host must not receive the runtime's ADC credentials.
     MockMcpToolset.assert_called_once_with(
         connection_params=StreamableHTTPConnectionParams(
             url="https://mcp.server1.com",
+            headers={},
+        ),
+        tool_filter=None,
+        tool_name_prefix=None,
+        header_provider=None,
+    )
+    self.assertEqual(toolset, MockMcpToolset.return_value)
+
+  @patch(
+      "google.adk.integrations.api_registry.api_registry.McpToolset",
+      autospec=True,
+  )
+  @patch("httpx.Client", autospec=True)
+  async def test_get_toolset_google_host_includes_credentials(
+      self, MockHttpClient, MockMcpToolset
+  ):
+    mock_response = MagicMock()
+    mock_response.raise_for_status = MagicMock()
+    mock_response.json = MagicMock(return_value=MOCK_MCP_SERVERS_LIST)
+    mock_client_instance = MockHttpClient.return_value
+    mock_client_instance.__enter__.return_value = mock_client_instance
+    mock_client_instance.get.return_value = mock_response
+
+    api_registry = ApiRegistry(
+        api_registry_project_id=self.project_id, location=self.location
+    )
+
+    toolset = api_registry.get_toolset("test-mcp-server-google")
+
+    # A Google API host receives the runtime's ADC credentials.
+    MockMcpToolset.assert_called_once_with(
+        connection_params=StreamableHTTPConnectionParams(
+            url="https://mcp.googleapis.com",
             headers={"Authorization": "Bearer mock_token"},
         ),
         tool_filter=None,
@@ -267,11 +305,11 @@ async def test_get_toolset_with_quota_project_id_success(
         api_registry_project_id=self.project_id, location=self.location
     )
 
-    toolset = api_registry.get_toolset("test-mcp-server-1")
+    toolset = api_registry.get_toolset("test-mcp-server-google")
 
     MockMcpToolset.assert_called_once_with(
         connection_params=StreamableHTTPConnectionParams(
-            url="https://mcp.server1.com",
+            url="https://mcp.googleapis.com",
             headers={
                 "Authorization": "Bearer mock_token",
                 "x-goog-user-project": "quota-project",
@@ -312,7 +350,7 @@ async def test_get_toolset_with_filter_and_prefix(
     MockMcpToolset.assert_called_once_with(
         connection_params=StreamableHTTPConnectionParams(
             url="https://mcp.server1.com",
-            headers={"Authorization": "Bearer mock_token"},
+            headers={},
         ),
         tool_filter=tool_filter,
         tool_name_prefix=tool_name_prefix,
@@ -348,7 +386,7 @@ def test_get_toolset_url_scheme(self):
           MockMcpToolset.assert_called_once_with(
               connection_params=StreamableHTTPConnectionParams(
                   url=mock_url,
-                  headers={"Authorization": "Bearer mock_token"},
+                  headers={},
               ),
               tool_filter=None,
               tool_name_prefix=None,