create_file · FastMCP Multi-Tool Server MCP: Risk & Policy

WHAT IT DOES

What create_file does on FastMCP Multi-Tool Server

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

WHY IT NEEDS A POLICY

Why create_file needs a policy

This tool creates new files, which is a reversible write operation. It does not delete or overwrite existing data (making it non-destructive), nor does it execute arbitrary code or manage financial transactions. The severity is medium because file creation could consume disk space or create malicious files if an AI misuses the tool, but the operation is reversible (files can be deleted).

From the tool's definition Tool name 'create_file' and description 'Create a new file with the specified content' clearly indicates file creation, which is a write operation that modifies the filesystem by adding new data.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

create_file Rate-limited

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": {
    "create_file": {
      "limits": [
        {
          "counter": "create_file_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 FastMCP Multi-Tool Server, so you can run agents against it safely.

FAQ

Questions about create_file

What does the create_file tool do? +

Create a new file with the specified content. It is categorised as a Write tool in the FastMCP Multi-Tool 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_file? +

Register the FastMCP Multi-Tool Server MCP server in PolicyLayer and add a rule for 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 FastMCP Multi-Tool Server. Nothing to install.

What risk level is create_file? +

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

Can I rate-limit create_file? +

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

Set action: deny in the PolicyLayer policy for 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 create_file? +

create_file is provided by the FastMCP Multi-Tool Server MCP server (rt0120-ramco/mcp-py). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.