Undo the last checkpoint (pops from stack and restores files). Each call removes the latest checkpoint from the stack. To undo multiple changes, call this function repeatedly until the desired state is reached.
AI agents use undo to create or update resources in Undo — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Undo environment.
This tool overwrites current file contents with previously saved checkpoint states. While it's reversible in principle (you could re-apply changes), it modifies files on disk and discards the current state of those files. It's primarily a Write/restore operation. Severity is high because misuse could overwrite significant work across multiple files, though the checkpoint system itself provides some safety net.
From the tool's definition 'pops from stack and restores files' — restores file states from checkpoints, modifying current file contents
Documented attack patterns abuse exactly the kind of access undo gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Undo, and nothing reaches the server without passing your rules. This is the rule we recommend for undo:
{
"version": "1",
"default": "deny",
"tools": {
"undo": {
"limits": [
{
"counter": "undo_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}undo stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
Free to start. No card required.
Undo the last checkpoint (pops from stack and restores files). Each call removes the latest checkpoint from the stack. To undo multiple changes, call this function repeatedly until the desired state is reached. It is categorised as a Write tool in the Undo MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Undo MCP server in PolicyLayer and add a rule for undo: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Undo. Nothing to install.
undo is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the undo rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for undo. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
undo is provided by the Undo MCP server (khalilbalaree/rewind-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Undo, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
5 Undo tools catalogued and risk-classified — across an index of 43,000+ MCP servers.