MANDATORY: ALWAYS call this function FIRST before making ANY file modifications, deletions, or creations. This creates a checkpoint to enable undo functionality. This must be called before every single file operation - no exceptions. Never modify files without calling checkpoint first.
AI agents use checkpoint 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.
The checkpoint tool writes checkpoint data to enable undo functionality. It does not execute arbitrary code, delete data, or move money. While it modifies the checkpoint store, this is a reversible metadata operation. The tool itself doesn't modify application files—it merely records their state.
From the tool's definition Tool creates snapshots/checkpoints of file states. Description states it 'creates a checkpoint' and 'snapshots file states before modifications'. This is a write operation that records data (file state snapshots) for recovery purposes.
Risk signalsBulk/mass operation — affects multiple targets
Documented attack patterns abuse exactly the kind of access checkpoint 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 checkpoint:
{
"version": "1",
"default": "deny",
"tools": {
"checkpoint": {
"limits": [
{
"counter": "checkpoint_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}checkpoint 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.
MANDATORY: ALWAYS call this function FIRST before making ANY file modifications, deletions, or creations. This creates a checkpoint to enable undo functionality. This must be called before every single file operation - no exceptions. Never modify files without calling checkpoint first. 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 checkpoint: 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.
checkpoint 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 checkpoint 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 checkpoint. 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.
checkpoint 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.