send_file_to_channel · Teams MCP: Risk & Policy

WHAT IT DOES

What send_file_to_channel does on Teams

AI agents use send_file_to_channel 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_channel needs a policy

The tool creates new data (a Teams message with an attachment) in a shared channel. This is a Write operation—it modifies the channel's message history reversibly. Severity is medium because unauthorized file uploads to shared channels could expose sensitive content or introduce malicious files, but the impact is limited to the target channel and messages remain deletable.

From the tool's definition "Upload a local file and send it as a message to a Teams channel" indicates the tool creates a new message object in the channel with an attached file. This is a reversible modification (the message can be deleted via delete_channel_message).

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

send_file_to_channel Rate-limited

send_file_to_channel 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_channel": {
      "limits": [
        {
          "counter": "send_file_to_channel_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 Teams, so you can run agents against it safely.

FAQ

Questions about send_file_to_channel

What does the send_file_to_channel tool do? +

Upload a local file and send it as a message to a Teams channel. Supports any file type (PDF, DOCX, ZIP, images, etc.). The file is uploaded to the channel. 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_channel? +

Register the Teams MCP server in PolicyLayer and add a rule for send_file_to_channel: 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_channel? +

send_file_to_channel 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_channel? +

Yes. Add a rate_limit block to the send_file_to_channel 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_channel completely? +

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

send_file_to_channel 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.