diff --git a/src/google/adk/cli/adk_web_server.py b/src/google/adk/cli/adk_web_server.py
index 86a2cf2495..f9520fff7c 100644
--- a/src/google/adk/cli/adk_web_server.py
+++ b/src/google/adk/cli/adk_web_server.py
@@ -997,7 +997,7 @@ async def version() -> dict[str, str]:
     @app.get("/list-apps")
     async def list_apps(
         detailed: bool = Query(
-            default=False, description="Return detailed app information"
+            default=True, description="Return detailed app information"
         )
     ) -> list[str] | ListAppsResponse:
       if detailed:
diff --git a/src/google/adk/cli/utils/agent_loader.py b/src/google/adk/cli/utils/agent_loader.py
index a7bbcbc2a6..5c3ad66073 100644
--- a/src/google/adk/cli/utils/agent_loader.py
+++ b/src/google/adk/cli/utils/agent_loader.py
@@ -364,13 +364,21 @@ def load_agent(self, agent_name: str) -> Union[BaseAgent, App]:
   def list_agents(self) -> list[str]:
     """Lists all agents available in the agent loader (sorted alphabetically)."""
     base_path = Path.cwd() / self.agents_dir
-    agent_names = [
-        x
-        for x in os.listdir(base_path)
-        if os.path.isdir(os.path.join(base_path, x))
-        and not x.startswith(".")
-        and x != "__pycache__"
-    ]
+    if not base_path.exists():
+      return []
+    agent_names = []
+    for x in os.listdir(base_path):
+      if x.startswith(".") or x == "__pycache__":
+        continue
+      agent_dir = base_path / x
+      if not agent_dir.is_dir():
+        continue
+      if (
+          (agent_dir / "root_agent.yaml").exists()
+          or (agent_dir / "agent.py").exists()
+          or (agent_dir / "__init__.py").exists()
+      ):
+        agent_names.append(x)
     agent_names.sort()
     return agent_names
 
diff --git a/tests/unittests/cli/test_fast_api.py b/tests/unittests/cli/test_fast_api.py
index 3e63f31222..538679621f 100755
--- a/tests/unittests/cli/test_fast_api.py
+++ b/tests/unittests/cli/test_fast_api.py
@@ -897,7 +897,7 @@ def test_app_with_a2a(
 def test_list_apps(test_app):
   """Test listing available applications."""
   # Use the TestClient to make a request
-  response = test_app.get("/list-apps")
+  response = test_app.get("/list-apps?detailed=false")
 
   # Verify the response
   assert response.status_code == 200
@@ -908,7 +908,7 @@ def test_list_apps(test_app):
 
 def test_list_apps_detailed(test_app):
   """Test listing available applications with detailed metadata."""
-  response = test_app.get("/list-apps?detailed=true")
+  response = test_app.get("/list-apps")
 
   assert response.status_code == 200
   data = response.json()
diff --git a/tests/unittests/cli/utils/test_agent_loader.py b/tests/unittests/cli/utils/test_agent_loader.py
index abc5718adb..1eb12b7ba7 100644
--- a/tests/unittests/cli/utils/test_agent_loader.py
+++ b/tests/unittests/cli/utils/test_agent_loader.py
@@ -1006,3 +1006,39 @@ def test_validate_agent_name_rejects_nonexistent_agent(self):
       # 'subprocess' is a valid identifier but shouldn't be importable as an agent
       with pytest.raises(ValueError, match="Agent not found"):
         loader.load_agent("subprocess")
+
+  def test_list_agents_ignores_non_agent_directories(self):
+    """Test that list_agents only returns directories containing valid agent files."""
+    with tempfile.TemporaryDirectory() as temp_dir:
+      temp_path = Path(temp_dir)
+      
+      # Create valid agent 1
+      agent1_dir = temp_path / "valid_agent1"
+      agent1_dir.mkdir()
+      (agent1_dir / "__init__.py").write_text("root_agent = None")
+      
+      # Create valid agent 2
+      agent2_dir = temp_path / "valid_agent2"
+      agent2_dir.mkdir()
+      (agent2_dir / "agent.py").write_text("root_agent = None")
+
+      # Create valid agent 3
+      agent3_dir = temp_path / "valid_agent3"
+      agent3_dir.mkdir()
+      (agent3_dir / "root_agent.yaml").write_text("name: test")
+      
+      # Create invalid directories
+      (temp_path / "utils").mkdir()
+      (temp_path / "data").mkdir()
+      (temp_path / "tmp").mkdir()
+      
+      loader = AgentLoader(str(temp_path))
+      agent_names = loader.list_agents()
+      
+      assert len(agent_names) == 3
+      assert "valid_agent1" in agent_names
+      assert "valid_agent2" in agent_names
+      assert "valid_agent3" in agent_names
+      assert "utils" not in agent_names
+      assert "data" not in agent_names
+