improve test coverage

Author: Walter Gillett

tests/test_mcp.py

@@ -1556,6 +1556,27 @@ def test_load_mcp_servers_partial_env_vars(tmp_path: Path, monkeypatch: pytest.M
     assert server.url == 'https://example.com/api/mcp'
 
 
+def test_load_mcp_servers_with_non_string_values(tmp_path: Path, monkeypatch: pytest.MonkeyPatch):
+    """Test that non-string primitive values (int, bool, null) in nested structures are passed through unchanged."""
+    config = tmp_path / 'mcp.json'
+
+    # Create a config with environment variables and extra fields containing primitives
+    # The extra fields will be ignored during validation but go through _expand_env_vars
+    monkeypatch.setenv('PYTHON_CMD', 'python')
+    config.write_text(
+        '{"mcpServers": {"my_server": {"command": "${PYTHON_CMD}", "args": ["-m", "tests.mcp_server"], '
+        '"metadata": {"count": 42, "enabled": true, "value": null}}}}'
+    )
+
+    # This should successfully expand env vars and ignore the metadata field
+    servers = load_mcp_servers(config)
+
+    assert len(servers) == 1
+    server = servers[0]
+    assert isinstance(server, MCPServerStdio)
+    assert server.command == 'python'
+
+
 async def test_server_info(mcp_server: MCPServerStdio) -> None:
     with pytest.raises(
         AttributeError, match='The `MCPServerStdio.server_info` is only instantiated after initialization.'