send_announcement · Slack MCP Server MCP: Risk & Policy

WHAT IT DOES

What send_announcement does on Slack MCP Server

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

WHY IT NEEDS A POLICY

Why send_announcement needs a policy

send_announcement creates/publishes new message content in Slack channels, making it a Write operation—it modifies data reversibly (messages can be deleted via delete_message tool on the same server). Severity is high because an AI agent could spam announcements, impersonate leadership, spread misinformation, or disrupt workflows across a workspace.

From the tool's definition Tool named 'send_announcement' on Slack MCP Server that enables messaging operations. Server description states it supports 'messaging' and 'all major Slack operations.' Sibling tools include 'send_message'-equivalent operations (implied by messaging…

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

send_announcement Rate-limited

send_announcement 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_announcement": {
      "limits": [
        {
          "counter": "send_announcement_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 Slack MCP Server, so you can run agents against it safely.

FAQ

Questions about send_announcement

What does the send_announcement tool do? +

send_announcement. It is categorised as a Write tool in the Slack 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 send_announcement? +

Register the Slack MCP Server MCP server in PolicyLayer and add a rule for send_announcement: 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 Slack MCP Server. Nothing to install.

What risk level is send_announcement? +

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

Can I rate-limit send_announcement? +

Yes. Add a rate_limit block to the send_announcement 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_announcement completely? +

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

send_announcement is provided by the Slack MCP Server MCP server (piekstra/slack-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.