add-attachment · Outlook MCP Server MCP: Risk & Policy

WHAT IT DOES

What add-attachment does on Outlook MCP Server

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

WHY IT NEEDS A POLICY

Why add-attachment needs a policy

This tool modifies email state by appending an attachment, which is a write operation. Severity is medium because while attachments can carry malicious payloads or sensitive data, the modification is confined to a draft email (not yet sent) and is reversible before the email is transmitted.

From the tool's definition Tool description states 'Adds a file attachment to an email message (typically a draft)' — this is a write operation that modifies an existing draft email by adding content to it. The action is reversible (attachment can be removed before sending).

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

add-attachment Rate-limited

add-attachment 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": {
    "add-attachment": {
      "limits": [
        {
          "counter": "add-attachment_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 Outlook MCP Server, so you can run agents against it safely.

FAQ

Questions about add-attachment

What does the add-attachment tool do? +

Adds a file attachment to an email message (typically a draft). It is categorised as a Write tool in the Outlook MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on add-attachment? +

Register the Outlook MCP Server MCP server in PolicyLayer and add a rule for add-attachment: 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 Outlook MCP Server. Nothing to install.

What risk level is add-attachment? +

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

Can I rate-limit add-attachment? +

Yes. Add a rate_limit block to the add-attachment 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 add-attachment completely? +

Set action: deny in the PolicyLayer policy for add-attachment. 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 add-attachment? +

add-attachment is provided by the Outlook MCP Server MCP server (peacockery-studio/outlook-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.