Update

Author: Scriptwonder

MCPForUnity/Editor/Tools/Prefabs/ManagePrefabs.cs

@@ -1170,7 +1170,7 @@ private static (int removedCount, ErrorResponse error) RemoveChildren(JToken del
                 string childPath = childToken.Type == JTokenType.String ? childToken.ToString() : childToken["name"]?.ToString();
                 if (string.IsNullOrEmpty(childPath))
                 {
-                    return (removedCount, new ErrorResponse("'delete_child' must be a string or object with 'name' field."));
+                    return (removedCount, new ErrorResponse("'deleteChild'/'delete_child' entries must be a string or object with 'name' field."));
                 }
 
                 // Find the child to remove

Server/src/cli/commands/prefab.py

@@ -256,8 +256,8 @@ def _parse_vector3(value: str) -> list[float]:
         raise click.BadParameter("Must be 'x,y,z' format")
     try:
         return [float(p.strip()) for p in parts]
-    except ValueError:
-        raise click.BadParameter(f"All components must be numeric, got: '{value}'")
+    except ValueError as e:
+        raise click.BadParameter(f"All components must be numeric, got: '{value}'") from e
 
 
 def _parse_property(prop_str: str) -> tuple[str, str, Any]:
@@ -268,7 +268,9 @@ def _parse_property(prop_str: str) -> tuple[str, str, Any]:
     if "." not in comp_prop:
         raise click.BadParameter("Must be 'Component.prop=value' format")
     component, prop = comp_prop.rsplit(".", 1)
-    
+    if not component.strip() or not prop.strip():
+        raise click.BadParameter(f"Component and property must be non-empty in '{comp_prop}', expected 'Component.prop=value'")
+
     val_str = val_str.strip()
 
     # Parse booleans
@@ -363,9 +365,12 @@ def modify(path: str, target: Optional[str], position: Optional[str], rotation:
         params["deleteChild"] = list(delete_child)
     if create_child:
         try:
-            params["createChild"] = json.loads(create_child)
+            parsed = json.loads(create_child)
         except json.JSONDecodeError as e:
             raise click.BadParameter(f"Invalid JSON for --create-child: {e}") from e
+        if not isinstance(parsed, dict):
+            raise click.BadParameter(f"--create-child must be a JSON object, got {type(parsed).__name__}")
+        params["createChild"] = parsed
 
     result = run_command("manage_prefabs", params, config)
     click.echo(format_output(result, config.format))

Server/tests/test_cli.py

@@ -732,6 +732,16 @@ def test_prefab_modify_invalid_create_child_json(self, runner, mock_unity_respon
             "--create-child", "not valid json"
         ])
         assert result.exit_code != 0
+        assert "Invalid JSON" in result.output
+
+    def test_prefab_modify_create_child_non_object_json(self, runner, mock_unity_response):
+        """Test prefab modify rejects non-object JSON for create-child."""
+        result = runner.invoke(cli, [
+            "prefab", "modify", "Assets/Prefabs/Player.prefab",
+            "--create-child", '"just a string"'
+        ])
+        assert result.exit_code != 0
+        assert "must be a JSON object" in result.output
 
     def test_prefab_modify_active_state(self, runner, mock_unity_response):
         """Test prefab modify active/inactive flag."""
@@ -805,6 +815,24 @@ def test_prefab_modify_set_property_string_value(self, runner, mock_unity_respon
             params = call_args[1]
             assert params["componentProperties"]["MyScript"]["label"] == "hello world"
 
+    def test_prefab_modify_set_property_empty_component(self, runner, mock_unity_response):
+        """Test prefab modify rejects empty component name in set-property."""
+        result = runner.invoke(cli, [
+            "prefab", "modify", "Assets/Prefabs/Player.prefab",
+            "--set-property", ".mass=5"
+        ])
+        assert result.exit_code != 0
+        assert "non-empty" in result.output
+
+    def test_prefab_modify_set_property_empty_prop(self, runner, mock_unity_response):
+        """Test prefab modify rejects empty property name in set-property."""
+        result = runner.invoke(cli, [
+            "prefab", "modify", "Assets/Prefabs/Player.prefab",
+            "--set-property", "Rigidbody.=5"
+        ])
+        assert result.exit_code != 0
+        assert "non-empty" in result.output
+
     def test_prefab_modify_no_options_sends_minimal_params(self, runner, mock_unity_response):
         """Test prefab modify with no options sends only action and prefabPath."""
         with patch("cli.commands.prefab.run_command", return_value=mock_unity_response) as mock_run: