send_channel_message · Teams MCP: Risk & Policy

WHAT IT DOES

What send_channel_message does on Teams

AI agents use send_channel_message 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_channel_message needs a policy

This tool creates new messages in Teams channels. While message creation is reversible (messages can be deleted via sibling tools like delete_channel_message), the primary action is to write/create data. The blast radius is medium because a misbehaving agent could spam channels, send misleading information, or @mention entire teams, but cannot directly delete data or cause financial harm.

From the tool's definition Tool description states 'Send a message to a specific channel' which creates new message data. The capability to send formatted messages with mentions and importance levels demonstrates irreversible content creation.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

send_channel_message Rate-limited

send_channel_message 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_channel_message": {
      "limits": [
        {
          "counter": "send_channel_message_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_channel_message

What does the send_channel_message tool do? +

Send a message to a specific channel in a Microsoft Team. Supports text and markdown formatting, mentions, and importance levels. 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_channel_message? +

Register the Teams MCP server in PolicyLayer and add a rule for send_channel_message: 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_channel_message? +

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

Can I rate-limit send_channel_message? +

Yes. Add a rate_limit block to the send_channel_message 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_channel_message completely? +

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

send_channel_message 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.