files_shared_public_url · Slack MCP: Risk & Policy

WHAT IT DOES

What files_shared_public_url does on Slack

AI agents use files_shared_public_url 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 files_shared_public_url needs a policy

This tool modifies the sharing state of a file by enabling public/external access. While technically reversible (sharing can be disabled), it represents a significant Write action that exposes files to external parties. It is not Destructive because the file itself is not deleted or overwritten, and not Execute because no arbitrary code/commands are run.

From the tool's definition Tool name 'files_shared_public_url' and description 'Enable a file for public/external sharing' indicate modification of file sharing settings, which changes data access permissions irreversibly until reversed.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

files_shared_public_url Rate-limited

files_shared_public_url 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": {
    "files_shared_public_url": {
      "limits": [
        {
          "counter": "files_shared_public_url_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 files_shared_public_url

What does the files_shared_public_url tool do? +

Enable a file for public/external sharing. 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 files_shared_public_url? +

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

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

Can I rate-limit files_shared_public_url? +

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

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

files_shared_public_url 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.