slack_send_message · MCP Slack Python MCP: Risk & Policy

WHAT IT DOES

What slack_send_message does on MCP Slack Python

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

WHY IT NEEDS A POLICY

Why slack_send_message needs a policy

Sending messages to Slack channels creates new data but does not irreversibly delete or modify existing content, execute arbitrary code, or move financial resources. This fits the Write category. Severity is medium because an agent misusing this could spam channels, impersonate users, send sensitive information, or disrupt team communication—but the effects are recoverable (messages can be deleted).

From the tool's definition Tool name 'slack_send_message' and description indicate it sends messages to Slack channels. This creates new message content in a workspace, which is a reversible write operation.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

slack_send_message Rate-limited

slack_send_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_send_message": {
      "limits": [
        {
          "counter": "slack_send_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 MCP Slack Python, so you can run agents against it safely.

FAQ

Questions about slack_send_message

What does the slack_send_message tool do? +

Slack 채널에 메시지 전송. It is categorised as a Write tool in the MCP Slack Python 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_send_message? +

Register the MCP Slack Python MCP server in PolicyLayer and add a rule for slack_send_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 MCP Slack Python. Nothing to install.

What risk level is slack_send_message? +

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

Can I rate-limit slack_send_message? +

Yes. Add a rate_limit block to the slack_send_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_send_message completely? +

Set action: deny in the PolicyLayer policy for slack_send_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_send_message? +

slack_send_message is provided by the MCP Slack Python MCP server (minji337/mcp-slack-python). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.