send_file_to_chat · Teams MCP: Risk & Policy

WHAT IT DOES

What send_file_to_chat does on Teams

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

WHY IT NEEDS A POLICY

Why send_file_to_chat needs a policy

This tool creates new message data in Teams chats by uploading files and attaching them. This is a reversible write operation—messages can be deleted and files removed. It does not execute code, delete data irreversibly, or move money. The severity is medium because misuse could flood chats with unwanted files, but the action is not irreversible and the blast radius is limited to a single chat or set of chats.

From the tool's definition The tool performs 'Upload a local file and send it as a message to a Teams chat.' This creates and modifies chat data by adding new file attachments to a conversation.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

send_file_to_chat Rate-limited

send_file_to_chat 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": {
    "send_file_to_chat": {
      "limits": [
        {
          "counter": "send_file_to_chat_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

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Instant setup, no code required.

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

FAQ

Questions about send_file_to_chat

What does the send_file_to_chat tool do? +

Upload a local file and send it as a message to a Teams chat. Supports any file type (PDF, DOCX, ZIP, images, etc.). The file is uploaded to OneDrive and sent as a reference attachment. It is categorised as a Write tool in the Teams MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on send_file_to_chat? +

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

What risk level is send_file_to_chat? +

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

Can I rate-limit send_file_to_chat? +

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

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

send_file_to_chat is provided by the Teams MCP server (@floriscornel/teams-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.