join_channel · Mcp Switchboard MCP: Risk & Policy

WHAT IT DOES

What join_channel does on Mcp Switchboard

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

WHY IT NEEDS A POLICY

Why join_channel needs a policy

This tool creates or modifies state in the inter-agent communication system by adding an agent to a channel. It is reversible (an agent can leave) and has no destructive, financial, or code execution components. The blast radius is minimal—worst case, an agent gains access to a communication channel it shouldn't have, but messages themselves are read-only from the agent's perspective post-join.

From the tool's definition Tool performs 'join a channel' action that modifies agent membership state in a coordination switchboard. The description indicates a state change (joining) with cursor initialization.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

join_channel Rate-limited

join_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.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "join_channel": {
      "limits": [
        {
          "counter": "join_channel_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 Switchboard, so you can run agents against it safely.

FAQ

Questions about join_channel

What does the join_channel tool do? +

Join a channel. Cursor starts at the current head (no history flood). It is categorised as a Write tool in the Mcp Switchboard MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on join_channel? +

Register the Mcp Switchboard MCP server in PolicyLayer and add a rule for join_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 Mcp Switchboard. Nothing to install.

What risk level is join_channel? +

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

Can I rate-limit join_channel? +

Yes. Add a rate_limit block to the join_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 join_channel completely? +

Set action: deny in the PolicyLayer policy for join_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 join_channel? +

join_channel is provided by the Mcp Switchboard MCP server (jemplayer82/mcp-switchboard). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.