copy_file · Nutstore MCP: Risk & Policy

WHAT IT DOES

What copy_file does on Nutstore

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

WHY IT NEEDS A POLICY

Why copy_file needs a policy

Copying files creates new data without destroying originals, making it a Write operation rather than Read (has side effects) or Destructive (original data remains). Severity is medium because a compromised copy operation could duplicate sensitive files or fill storage quota, but the effects remain recoverable and no financial impact occurs.

From the tool's definition Tool description states '复制坚果云中的文件或目录' (copy files or directories in Nutstore cloud storage). The copy operation creates new data objects in the storage system, which is a reversible modification.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

copy_file Rate-limited

copy_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": {
    "copy_file": {
      "limits": [
        {
          "counter": "copy_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 Nutstore, so you can run agents against it safely.

FAQ

Questions about copy_file

What does the copy_file tool do? +

复制坚果云中的文件或目录. It is categorised as a Write tool in the Nutstore MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on copy_file? +

Register the Nutstore MCP server in PolicyLayer and add a rule for copy_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 Nutstore. Nothing to install.

What risk level is copy_file? +

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

Can I rate-limit copy_file? +

Yes. Add a rate_limit block to the copy_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 copy_file completely? +

Set action: deny in the PolicyLayer policy for copy_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 copy_file? +

copy_file is provided by the Nutstore MCP server (silverze/nutstore-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.