slack_send · Access MCP: Risk & Policy

WHAT IT DOES

What slack_send does on Access

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

WHY IT NEEDS A POLICY

Why slack_send needs a policy

slack_send creates new data (messages) that is immediately persisted and visible. While reversible (messages can be deleted), it has moderate blast radius: an agent could spam channels, leak sensitive information, or impersonate users through unintended message composition.

From the tool's definition Tool description states 'Send a Slack message to a channel, DM, or thread' with side effect of 'delivers the message immediately and it is visible to all channel members.' This is a create/post action that modifies state (adds a message to Slack) reversibly.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

slack_send Rate-limited

slack_send 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": {
    "slack_send": {
      "limits": [
        {
          "counter": "slack_send_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 Access, so you can run agents against it safely.

FAQ

Questions about slack_send

What does the slack_send tool do? +

Send a Slack message to a channel, DM, or thread. Side effect: delivers the message immediately and it is visible to all channel members. Supports Slack mrkdwn formatting. It is categorised as a Write tool in the Access MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on slack_send? +

Register the Access MCP server in PolicyLayer and add a rule for slack_send: 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 Access. Nothing to install.

What risk level is slack_send? +

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

Can I rate-limit slack_send? +

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

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

slack_send is provided by the Access MCP server (scottpedia0/access). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.