fs_apply_patch_with_backup · LocalAnt MCP: Risk & Policy

WHAT IT DOES

What fs_apply_patch_with_backup does on LocalAnt

AI agents use fs_apply_patch_with_backup to create or update resources in LocalAnt — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your LocalAnt environment.

WHY IT NEEDS A POLICY

Why fs_apply_patch_with_backup needs a policy

This tool modifies file content (Write operation). Although it creates a backup for potential recovery, it irreversibly changes the current state of a file—a high-severity action if misapplied by an AI agent to critical system or application files.

From the tool's definition Tool name 'fs_apply_patch_with_backup' and description 'Replace an existing file' indicate modification of file contents. The '_with_backup' suffix suggests reversibility through backup restoration, distinguishing this from Destructive category.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

fs_apply_patch_with_backup Rate-limited

fs_apply_patch_with_backup 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.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "fs_apply_patch_with_backup": {
      "limits": [
        {
          "counter": "fs_apply_patch_with_backup_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches LocalAnt, so you can run agents against it safely.

FAQ

Questions about fs_apply_patch_with_backup

What does the fs_apply_patch_with_backup tool do? +

Replace an existing file. It is categorised as a Write tool in the LocalAnt MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on fs_apply_patch_with_backup? +

Register the LocalAnt MCP server in PolicyLayer and add a rule for fs_apply_patch_with_backup: 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 LocalAnt. Nothing to install.

What risk level is fs_apply_patch_with_backup? +

fs_apply_patch_with_backup is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit fs_apply_patch_with_backup? +

Yes. Add a rate_limit block to the fs_apply_patch_with_backup 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.

How do I block fs_apply_patch_with_backup completely? +

Set action: deny in the PolicyLayer policy for fs_apply_patch_with_backup. 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.

What MCP server provides fs_apply_patch_with_backup? +

fs_apply_patch_with_backup is provided by the LocalAnt MCP server (yuga-hashimoto/localant). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.