---
title: "tool si.act.undo"
description: "a done action: the action, undone, and the inverse's own action."
section: reference
address: /reference/tools/si-act-undo
contract: 0476e35e6e275db5
---

# tool si.act.undo

a done action: the action, undone, and the inverse's own action.

[figure: Over MCP, si.act.undo takes UndoInput and returns a card whose body is UndoAnswer.]

the action, undone, and the inverse's own action. The call needs the act grant at the strategy rung.



| | |
|---|---|
| input | [UndoInput](/concepts/undoinput) |
| result | a card whose body is [UndoAnswer](/concepts/undoanswer) |
| read-only | no |
| destructive | yes |
| card address | `ui://scale-intelligence/cards/UndoAnswer` |
| HTTP route | [`/v1/act/undo`](/reference/act/undo) |





| field | type | required | note |
|---|---|---|---|
| `action` | `id` | yes |  |
| `reason` | `text` | yes |  |