Overview
The undo tool reverts the last recorded action in Roblox Studio’s change history. This is equivalent to pressing Ctrl+Z in Studio and allows AI assistants to undo mistakes or unwanted changes programmatically.
Use Cases
- Revert accidental changes or mistakes
- Step back through experimental modifications
- Implement trial-and-error workflows
- Undo automated operations that had unexpected results
- Allow users to revert AI-generated changes
- Test changes and easily roll back
- Provide “undo last action” functionality in tools
Parameters
This tool takes no parameters.
Response Structure
Whether the undo operation succeeded
Description of the result (e.g., “Undo successful” or “Nothing to undo”)
Example Response (Success)
{
"success": true,
"message": "Undo successful"
}
Example Response (Nothing to Undo)
{
"success": false,
"message": "Nothing to undo"
}
Usage Examples
Basic Undo
// Undo the last action
const result = await mcpClient.callTool('undo', {});
if (result.success) {
console.log('Last action undone');
} else {
console.log('Nothing to undo');
}
Undo After Mistake
// Try an operation, undo if it fails
try {
await mcpClient.callTool('set_property', {
instancePath: 'game.Workspace.Part',
propertyName: 'Size',
propertyValue: { X: 10, Y: 10, Z: 10 }
});
// Check if the change looks good
const props = await mcpClient.callTool('get_instance_properties', {
instancePath: 'game.Workspace.Part'
});
if (props.Size.X > 100) {
console.log('Size too large, undoing...');
await mcpClient.callTool('undo', {});
}
} catch (error) {
console.log('Operation failed, undoing...');
await mcpClient.callTool('undo', {});
}
Multiple Undos
// Undo the last 3 actions
for (let i = 0; i < 3; i++) {
const result = await mcpClient.callTool('undo', {});
if (result.success) {
console.log(`Undone action ${i + 1}`);
} else {
console.log('No more actions to undo');
break;
}
}
Experimental Workflow
// Try something, ask user if they like it, undo if not
await mcpClient.callTool('mass_set_property', {
paths: platformPaths,
propertyName: 'BrickColor',
propertyValue: 'Really red'
});
console.log('All platforms are now red.');
const keepChanges = await askUser('Keep these changes? (yes/no)');
if (keepChanges === 'no') {
await mcpClient.callTool('undo', {});
console.log('Changes reverted');
}
Trial and Error
// Try different values until one works
const testValues = [10, 20, 30, 40, 50];
for (const value of testValues) {
// Try this value
await mcpClient.callTool('set_property', {
instancePath: 'game.Workspace.Part',
propertyName: 'Size',
propertyValue: { X: value, Y: 1, Z: 4 }
});
// Test if it works
const isValid = await validateSize(value);
if (isValid) {
console.log(`Found valid size: ${value}`);
break;
} else {
// Undo and try next value
await mcpClient.callTool('undo', {});
}
}
Undo Batch Operations
// Perform batch operation with undo safety
const initialState = await captureState();
try {
// Perform complex operation
await mcpClient.callTool('mass_set_property', {
paths: manyPaths,
propertyName: 'Transparency',
propertyValue: 0.5
});
// Validate results
const validationPassed = await validateChanges();
if (!validationPassed) {
console.log('Validation failed, undoing...');
await mcpClient.callTool('undo', {});
}
} catch (error) {
console.error('Operation failed:', error);
await mcpClient.callTool('undo', {});
}
Interactive Undo
// Let user undo recent actions
console.log('Recent actions:');
console.log('1. Created 10 platforms');
console.log('2. Changed colors to red');
console.log('3. Moved platforms');
const undoCount = await askUser('How many actions to undo?');
for (let i = 0; i < undoCount; i++) {
const result = await mcpClient.callTool('undo', {});
if (!result.success) {
console.log(`Undone ${i} actions (no more history)`);
break;
}
}
console.log('Undo complete');
Tips and Best Practices
Not all operations are recorded in change history. Script changes via ScriptEditorService are recorded, but some API operations may not be.
Studio’s undo history has a limit. Very old actions may no longer be available to undo.
Calling undo multiple times will step back through history. Be careful not to undo more than intended.
Combine undo with user confirmation dialogs for safe experimentation. Make changes, show the result, then undo if the user doesn’t approve.
Behavior Details
What Can Be Undone
- Property changes (set_property, mass_set_property)
- Object creation (create_object, etc.)
- Object deletion (delete_object)
- Object reparenting (reparent_object, mass_reparent)
- Script source changes (set_script_source, edit_script_lines)
- Grouping/ungrouping operations
- Most operations that modify the game state
What Cannot Be Undone
- Reading operations (get_property, get_script_source) - nothing to undo
- Some internal API calls that don’t record history
- Changes made directly in Studio (outside MCP)
- Plugin-specific operations that don’t use ChangeHistoryService
History Stack
- Undo removes the most recent action from history
- After undo, that action can be redone with
redo
- Performing a new action after undo clears the redo stack
- History has a maximum depth (varies by Studio)
Undo Waypoints
- Studio records changes as “waypoints” in history
- Some operations may create multiple waypoints
- Undo reverts to the previous waypoint
Common Patterns
Try-Catch-Undo
try {
await performRiskyOperation();
} catch (error) {
await mcpClient.callTool('undo', {});
throw error;
}
Validate-Then-Undo
await makeChange();
const isValid = await validate();
if (!isValid) {
await mcpClient.callTool('undo', {});
}
User-Controlled Undo
const actions = [];
for (const action of actions) {
await performAction(action);
const keepIt = await askUser('Keep this change?');
if (!keepIt) {
await mcpClient.callTool('undo', {});
}
}
Undo Until Condition
while (await someConditionIsMet()) {
const result = await mcpClient.callTool('undo', {});
if (!result.success) {
break; // No more history
}
}
Common Issues
Issue: Undo doesn’t seem to work
- The operation may not have been recorded in change history
- Some API calls don’t create undo waypoints
- Verify that there is actually history to undo (check response message)
Issue: Undo undoes too much
- Some operations create multiple waypoints
- Use redo to step forward if you undo too far
- Consider saving state before operations instead of relying on undo
Issue: Nothing to undo message
- There is no recorded history to undo
- All history may have been exhausted
- The history stack may have been cleared
Issue: Undo doesn’t work for specific operations
- Not all operations are recorded in ChangeHistoryService
- Direct Lua operations may not create waypoints
- Some plugin-specific operations don’t integrate with Studio undo
