list_channels

THE RISK

Low Risk

Why list_channels needs a policy

This tool only retrieves information about available channels without creating, modifying, or deleting any data. It has no impact on system state and represents a straightforward informational query, making it a Read-category tool with low severity.

From the tool's definition Tool name is 'list_channels' and description indicates it 'List all channels you could join' - a query operation with no side effects. The incomplete description ('shows which ones you') suggests it retrieves and displays channel information.

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

POLICY

How to control list_channels

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 list_channels:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "list_channels": {}
  }
}

list_channels is read-only, so it stays allowed — but 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.

CAP THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More Claude Slack tools

Write leave_channel Leave a channel. You will no longer recieve messages from this channel. 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

All 19 Claude Slack tools →

Read tools on other servers

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Data exfiltration → How read access becomes an exfiltration channel when chained with untrusted content.
MCP token cost → What connecting this server costs in context-window tokens on every request.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about list_channels

What does the list_channels tool do? +

List all channels you could join (shows which ones you. It is categorised as a Read tool in the Claude Slack MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on list_channels? +

Register the Claude Slack MCP server in PolicyLayer and add a rule for list_channels: 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 list_channels? +

list_channels is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit list_channels? +

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

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

list_channels 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 →