copy_object · Rustfs MCP: Risk & Policy

WHAT IT DOES

What copy_object does on Rustfs

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

WHY IT NEEDS A POLICY

Why copy_object needs a policy

This tool creates a new object (copy operation), which is a reversible modification of data. While copies can be deleted later, the operation itself adds new data to the S3-compatible bucket. This is Write-category behavior. Severity is high because unrestricted copying could exhaust storage quotas, incur costs, or expose sensitive data across multiple object locations.

From the tool's definition Tool description states 'Server-side copy an object' which modifies the object storage by creating a new copy of an object.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

copy_object Rate-limited

copy_object 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_object": {
      "limits": [
        {
          "counter": "copy_object_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 Rustfs, so you can run agents against it safely.

FAQ

Questions about copy_object

What does the copy_object tool do? +

Server-side copy an object. (Refused on read-only / production add-ons.). It is categorised as a Write tool in the Rustfs 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_object? +

Register the Rustfs MCP server in PolicyLayer and add a rule for copy_object: 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 Rustfs. Nothing to install.

What risk level is copy_object? +

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

Can I rate-limit copy_object? +

Yes. Add a rate_limit block to the copy_object 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_object completely? +

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

copy_object is provided by the Rustfs MCP server (stackblaze/rustfs-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.