leave_channel

THE RISK

Medium Risk

Why leave_channel needs a policy

Leaving a channel modifies the agent's subscription/membership state — it removes the agent from the channel so it no longer receives messages. This is a reversible state change (the agent could rejoin via join_channel), making it Write rather than Destructive. Misuse could disrupt multi-agent collaboration workflows by cutting off communication, hence medium severity.

From the tool's definition Leave a channel. You will no longer receive messages from this channel.

Documented attack patterns abuse exactly the kind of access leave_channel gives an agent:

POLICY

How to control leave_channel

PolicyLayer is an MCP gateway — it sits between your AI agents and Claude Slack, and nothing reaches the server without passing your rules. This is the rule we recommend for leave_channel:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "leave_channel": {
      "limits": [
        {
          "counter": "leave_channel_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

leave_channel 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.

Create a free account and register Claude Slack — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More Claude Slack tools

Write create_channel Create a new channel for topic-based discussions Write send_channel_message Send a message to a channel (only agents who are members of this channel will receive it) Write send_direct_message Send a private message to another agent Write write_note Save a note for your future self - findings, solutions, gotchas, etc. TIP: Write notes aft Read get_current_project Get information about the current project context Read get_linked_projects View which projects are linked to the current project (read-only) Read get_messages Check for new messages from your channels and DMs, or get specific messages by ID. TIP: Ca Read get_performance_stats Get performance statistics for debugging slow tool calls

All 19 Claude Slack tools →

Write tools on other servers

M-Team MCP Server download_torrent YouTube MCP Server generate_video_title Android Forensics ADB MCP Server combine_reports 0xarchive web3_signup

Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Argument validation → Checking tool call arguments against schema and policy before they run.
Scoped token → Per-person credentials that grant a defined subset of servers and tools.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about leave_channel

What does the leave_channel tool do? +

Leave a channel. You will no longer recieve messages from this channel. It is categorised as a Write tool in the Claude 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 leave_channel? +

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

What risk level is leave_channel? +

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

Can I rate-limit leave_channel? +

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

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

leave_channel is provided by the Claude Slack MCP server (theo-nash/claude-slack). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Claude Slack tool call.

Start from Claude Slack, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →