files_move · Pyfastmail MCP: Risk & Policy

WHAT IT DOES

What files_move does on Pyfastmail

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

WHY IT NEEDS A POLICY

Why files_move needs a policy

The tool modifies file/folder metadata (location, name) within the user's Fastmail storage but does not irreversibly delete data. Moving and renaming are reversible operations (files can be moved back or renamed again). This qualifies as Write rather than Destructive.

From the tool's definition Tool description states 'Move or rename a file or folder on Fastmail Files (WebDAV)' — this modifies the state and location of files/folders, which is a reversible write operation.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

files_move Rate-limited

files_move 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": {
    "files_move": {
      "limits": [
        {
          "counter": "files_move_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 Pyfastmail, so you can run agents against it safely.

FAQ

Questions about files_move

What does the files_move tool do? +

Move or rename a file or folder on Fastmail Files (WebDAV). It is categorised as a Write tool in the Pyfastmail MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on files_move? +

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

What risk level is files_move? +

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

Can I rate-limit files_move? +

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

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

files_move is provided by the Pyfastmail MCP server (pjosols/pyfastmail-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.