create_directory · Filesystem MCP Server MCP: Risk & Policy

WHAT IT DOES

What create_directory does on Filesystem MCP Server

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

WHY IT NEEDS A POLICY

Why create_directory needs a policy

Creating directories is a reversible filesystem modification that creates new data structures. It does not irreversibly delete data (would be Destructive), nor does it execute arbitrary code (would be Execute). While it modifies the filesystem, it is categorized as Write rather than higher severity because directory creation can be undone by deletion.

From the tool's definition Tool description states 'Create a new directory' which is a write operation that modifies filesystem state. The server description confirms it provides 'write' capabilities including 'create' operations.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

create_directory Rate-limited

create_directory 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": {
    "create_directory": {
      "limits": [
        {
          "counter": "create_directory_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 Filesystem MCP Server, so you can run agents against it safely.

FAQ

Questions about create_directory

What does the create_directory tool do? +

Create a new directory, including parent directories if needed. It is categorised as a Write tool in the Filesystem MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on create_directory? +

Register the Filesystem MCP Server MCP server in PolicyLayer and add a rule for create_directory: 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 Filesystem MCP Server. Nothing to install.

What risk level is create_directory? +

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

Can I rate-limit create_directory? +

Yes. Add a rate_limit block to the create_directory 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 create_directory completely? +

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

create_directory is provided by the Filesystem MCP Server MCP server (njbrake/filesystem-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.