open_conversation · Slack MCP Server MCP: Risk & Policy

WHAT IT DOES

What open_conversation does on Slack MCP Server

AI agents use open_conversation 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 open_conversation needs a policy

Opening a DM conversation is a reversible write operation—it creates a new conversation record or modifies existing state without deleting data or executing code. While it doesn't permanently alter data like Destructive actions, it does modify Slack's state by establishing a new communication channel.

From the tool's definition Tool description states it will "open or resume a direct message conversation." The verb "open" indicates initiation of a communication channel, and "resume" suggests state modification. This creates or modifies the conversation state in Slack.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

open_conversation Rate-limited

open_conversation 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": {
    "open_conversation": {
      "limits": [
        {
          "counter": "open_conversation_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 Slack MCP Server, so you can run agents against it safely.

FAQ

Questions about open_conversation

What does the open_conversation tool do? +

Open or resume a direct message conversation. 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 open_conversation? +

Register the Slack MCP Server MCP server in PolicyLayer and add a rule for open_conversation: 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 open_conversation? +

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

Can I rate-limit open_conversation? +

Yes. Add a rate_limit block to the open_conversation 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 open_conversation completely? +

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

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