fix: Only prepend "https://" to the MCP server url if it doesn't already have a scheme

There isn't a consistent format for MCP server urls in the registry-- some customers add the https:// but others don't. To standardize, only prepend if it isn't there already.

Co-authored-by: Kathy Wu <wukathy@google.com>
PiperOrigin-RevId: 846451152

src/google/adk/tools/api_registry.py

@@ -102,9 +102,13 @@ class ApiRegistry:
     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
+
     return McpToolset(
         connection_params=StreamableHTTPConnectionParams(
-            url="https://" + mcp_server_url,
+            url=mcp_server_url,
             headers=headers,
         ),
         tool_filter=tool_filter,

tests/unittests/tools/test_api_registry.py

@@ -18,6 +18,7 @@ from unittest.mock import create_autospec
 from unittest.mock import MagicMock
 from unittest.mock import patch
 
+from google.adk.tools import api_registry
 from google.adk.tools.api_registry import ApiRegistry
 from google.adk.tools.mcp_tool.mcp_session_manager import StreamableHTTPConnectionParams
 import httpx
@@ -35,6 +36,14 @@ MOCK_MCP_SERVERS_LIST = {
         {
             "name": "test-mcp-server-no-url",
         },
+        {
+            "name": "test-mcp-server-http",
+            "urls": ["http://mcp.server_http.com"],
+        },
+        {
+            "name": "test-mcp-server-https",
+            "urls": ["https://mcp.server_https.com"],
+        },
     ]
 }
 
@@ -70,10 +79,12 @@ class TestApiRegistry(unittest.IsolatedAsyncioTestCase):
         api_registry_project_id=self.project_id, location=self.location
     )
 
-    self.assertEqual(len(api_registry._mcp_servers), 3)
+    self.assertEqual(len(api_registry._mcp_servers), 5)
     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)
+    self.assertIn("test-mcp-server-http", api_registry._mcp_servers)
+    self.assertIn("test-mcp-server-https", api_registry._mcp_servers)
     mock_client_instance.get.assert_called_once_with(
         f"https://cloudapiregistry.googleapis.com/v1beta/projects/{self.project_id}/locations/{self.location}/mcpServers",
         headers={
@@ -95,10 +106,12 @@ class TestApiRegistry(unittest.IsolatedAsyncioTestCase):
         api_registry_project_id=self.project_id, location=self.location
     )
 
-    self.assertEqual(len(api_registry._mcp_servers), 3)
+    self.assertEqual(len(api_registry._mcp_servers), 5)
     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)
+    self.assertIn("test-mcp-server-http", api_registry._mcp_servers)
+    self.assertIn("test-mcp-server-https", api_registry._mcp_servers)
     mock_client_instance.get.assert_called_once_with(
         f"https://cloudapiregistry.googleapis.com/v1beta/projects/{self.project_id}/locations/{self.location}/mcpServers",
         headers={
@@ -232,6 +245,41 @@ class TestApiRegistry(unittest.IsolatedAsyncioTestCase):
     )
     self.assertEqual(toolset, MockMcpToolset.return_value)
 
+  def test_get_toolset_url_scheme(self):
+    params = [
+        ("test-mcp-server-http", "http://mcp.server_http.com"),
+        ("test-mcp-server-https", "https://mcp.server_https.com"),
+    ]
+    for mock_server_name, mock_url in params:
+      with self.subTest(server_name=mock_server_name):
+        with (
+            patch.object(httpx, "Client", autospec=True) as MockHttpClient,
+            patch.object(
+                api_registry, "McpToolset", autospec=True
+            ) as MockMcpToolset,
+        ):
+          mock_response = create_autospec(httpx.Response, instance=True)
+          mock_response.json.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_instance = ApiRegistry(
+              api_registry_project_id=self.project_id, location=self.location
+          )
+
+          api_registry_instance.get_toolset(mock_server_name)
+
+          MockMcpToolset.assert_called_once_with(
+              connection_params=StreamableHTTPConnectionParams(
+                  url=mock_url,
+                  headers={"Authorization": "Bearer mock_token"},
+              ),
+              tool_filter=None,
+              tool_name_prefix=None,
+              header_provider=None,
+          )
+
   @patch("httpx.Client", autospec=True)
   async def test_get_toolset_server_not_found(self, MockHttpClient):
     mock_response = MagicMock()