unshare_file · Mail Cal Drive MCP: Risk & Policy

WHAT IT DOES

What unshare_file does on Mail Cal Drive

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

WHY IT NEEDS A POLICY

Why unshare_file needs a policy

Removing sharing permissions modifies access control on a file. While this is reversible (permissions can be re-granted), it can have significant impact by immediately cutting off access for users or groups who relied on that share. It's a Write action (modifying permissions), not Destructive since the file itself is not deleted and the action can be undone by re-sharing.

From the tool's definition "Remove sharing permission from a file"

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

unshare_file Rate-limited

unshare_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": {
    "unshare_file": {
      "limits": [
        {
          "counter": "unshare_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 Mail Cal Drive, so you can run agents against it safely.

FAQ

Questions about unshare_file

What does the unshare_file tool do? +

Remove sharing permission from a file. It is categorised as a Write tool in the Mail Cal Drive MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on unshare_file? +

Register the Mail Cal Drive MCP server in PolicyLayer and add a rule for unshare_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 Mail Cal Drive. Nothing to install.

What risk level is unshare_file? +

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

Can I rate-limit unshare_file? +

Yes. Add a rate_limit block to the unshare_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 unshare_file completely? +

Set action: deny in the PolicyLayer policy for unshare_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 unshare_file? +

unshare_file is provided by the Mail Cal Drive MCP server (rumbitopi/mail-cal-drive-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.