mkdir · MCP File System Server MCP: Risk & Policy

WHAT IT DOES

What mkdir does on MCP File System Server

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

WHY IT NEEDS A POLICY

Why mkdir needs a policy

Creating a directory modifies the file system by adding new structure, which qualifies as a Write action. The operation is reversible (the directory can be deleted later), so it does not rise to Destructive severity.

From the tool's definition Tool name 'mkdir' and description 'Create a directory' indicate directory creation, a reversible write operation.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

mkdir Rate-limited

mkdir 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": {
    "mkdir": {
      "limits": [
        {
          "counter": "mkdir_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 MCP File System Server, so you can run agents against it safely.

FAQ

Questions about mkdir

What does the mkdir tool do? +

Create a directory. It is categorised as a Write tool in the MCP File System 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 mkdir? +

Register the MCP File System Server MCP server in PolicyLayer and add a rule for mkdir: 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 MCP File System Server. Nothing to install.

What risk level is mkdir? +

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

Can I rate-limit mkdir? +

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

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

mkdir is provided by the MCP File System Server MCP server (kvas-it/mcp-server-fs). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.