slack_post_message · Server Puppeteer MCP: Risk & Policy

WHAT IT DOES

What slack_post_message does on Server Puppeteer

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

WHY IT NEEDS A POLICY

Why slack_post_message needs a policy

This tool creates new content in Slack, which is a reversible action (messages can be edited or deleted). It does not execute arbitrary code, destroy data irreversibly, or move money. The severity is medium because misuse could spam channels, leak sensitive information, or disrupt team communication, but the blast radius is limited to message creation rather than system-wide effects.

From the tool's definition Tool name 'slack_post_message' and description 'Post a new message to a Slack channel' indicate creation of new data (a message) in an external service (Slack).

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

slack_post_message Rate-limited

slack_post_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": {
    "slack_post_message": {
      "limits": [
        {
          "counter": "slack_post_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 Server Puppeteer, so you can run agents against it safely.

FAQ

Questions about slack_post_message

What does the slack_post_message tool do? +

Post a new message to a Slack channel. It is categorised as a Write tool in the Server Puppeteer MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on slack_post_message? +

Register the Server Puppeteer MCP server in PolicyLayer and add a rule for slack_post_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 Server Puppeteer. Nothing to install.

What risk level is slack_post_message? +

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

Can I rate-limit slack_post_message? +

Yes. Add a rate_limit block to the slack_post_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 slack_post_message completely? +

Set action: deny in the PolicyLayer policy for slack_post_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 slack_post_message? +

slack_post_message is provided by the Server Puppeteer MCP server (@hisma/server-puppeteer). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.