update_file · Microsoft MCP: Risk & Policy

WHAT IT DOES

What update_file does on Microsoft MCP

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

WHY IT NEEDS A POLICY

Why update_file needs a policy

The tool creates or modifies data reversibly by updating file content in OneDrive. While the blast radius is significant (an AI agent could overwrite important documents), the action is not irreversible due to OneDrive's version control and recovery capabilities. Severity is 'high' because uncontrolled file updates could corrupt critical business documents, but not 'critical' because recovery mechanisms exist.

From the tool's definition Tool name 'update_file' and description 'Update OneDrive file content from a local file' indicate modification of existing data in OneDrive. This is reversible (files can be restored from version history in OneDrive), distinguishing it from Destructive.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

update_file Rate-limited

update_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": {
    "update_file": {
      "limits": [
        {
          "counter": "update_file_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

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PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Microsoft MCP, so you can run agents against it safely.

FAQ

Questions about update_file

What does the update_file tool do? +

Update OneDrive file content from a local file. It is categorised as a Write tool in the Microsoft MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on update_file? +

Register the Microsoft MCP server in PolicyLayer and add a rule for update_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 Microsoft MCP. Nothing to install.

What risk level is update_file? +

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

Can I rate-limit update_file? +

Yes. Add a rate_limit block to the update_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 update_file completely? +

Set action: deny in the PolicyLayer policy for update_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 update_file? +

update_file is provided by the Microsoft MCP server (purva-kashyap/microsoft-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.