chat_command · Slack MCP: Risk & Policy

WHAT IT DOES

What chat_command does on Slack

AI agents invoke chat_command to trigger actions in Slack. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

WHY IT NEEDS A POLICY

Why chat_command needs a policy

This tool runs slash commands in Slack, which can execute arbitrary operations depending on what commands are configured in the workspace. The actual effects depend on which slash commands exist and what they do, making this an Execute category tool rather than a simple Read or Write operation. The 'legacy undocumented' qualifier suggests limited visibility into its behavior, which increases risk.

From the tool's definition Tool name 'chat_command' combined with description 'Execute a slash command (legacy undocumented)'. The word 'Execute' directly indicates code/command execution capability.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

chat_command Rate-limited

chat_command stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "chat_command": {
      "limits": [
        {
          "counter": "chat_command_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-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 chat_command

What does the chat_command tool do? +

Execute a slash command (legacy undocumented). It is categorised as a Execute tool in the Slack MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on chat_command? +

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

chat_command is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit chat_command? +

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

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

chat_command 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.