conversations_open · Slack MCP: Risk & Policy

WHAT IT DOES

What conversations_open does on Slack

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

WHY IT NEEDS A POLICY

Why conversations_open needs a policy

The 'open' action on Slack conversations creates a new DM or conversation thread, which is a reversible write operation. While the description is empty (lowering confidence slightly), the tool name and context of the Slack MCP server—which provides message and channel management—indicate this creates new conversational objects.

From the tool's definition Tool name 'conversations_open' on Slack MCP server. Slack's conversations.open API creates or initiates direct message conversations, which modifies workspace state by establishing new message threads.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

conversations_open Rate-limited

conversations_open 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": {
    "conversations_open": {
      "limits": [
        {
          "counter": "conversations_open_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, so you can run agents against it safely.

FAQ

Questions about conversations_open

What does the conversations_open tool do? +

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

How do I enforce a policy on conversations_open? +

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

What risk level is conversations_open? +

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

Can I rate-limit conversations_open? +

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

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

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