fs_create_file · LocalAnt MCP: Risk & Policy

WHAT IT DOES

What fs_create_file does on LocalAnt

AI agents use fs_create_file 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_create_file needs a policy

This tool creates or modifies files, which is a reversible write operation. While a backup is maintained on overwrite, the primary function is file creation/modification rather than irreversible deletion.

From the tool's definition Tool name 'fs_create_file' and description 'Create a file, optionally overwriting (a backup is kept on overwrite)' indicate file creation and modification capability.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

fs_create_file Rate-limited

fs_create_file 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_create_file": {
      "limits": [
        {
          "counter": "fs_create_file_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

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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_create_file

What does the fs_create_file tool do? +

Create a file, optionally overwriting (a backup is kept on overwrite). 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_create_file? +

Register the LocalAnt MCP server in PolicyLayer and add a rule for fs_create_file: 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_create_file? +

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

Can I rate-limit fs_create_file? +

Yes. Add a rate_limit block to the fs_create_file 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_create_file completely? +

Set action: deny in the PolicyLayer policy for fs_create_file. 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_create_file? +

fs_create_file 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.