functions_complete_error · Slack MCP: Risk & Policy

WHAT IT DOES

What functions_complete_error does on Slack

AI agents use functions_complete_error 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 functions_complete_error needs a policy

This tool modifies state by marking a function as failed (vs. completed), which is a reversible write operation that updates metadata/records in Slack. While not directly creating/modifying message content or user data, it performs an irreversible business logic state transition.

From the tool's definition Tool description states 'Signal that a function failed' - this writes an error status/state change to Slack's function execution system, creating or modifying record of a function's completion status.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

functions_complete_error Rate-limited

functions_complete_error 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": {
    "functions_complete_error": {
      "limits": [
        {
          "counter": "functions_complete_error_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 functions_complete_error

What does the functions_complete_error tool do? +

Signal that a function failed to complete. 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 functions_complete_error? +

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

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

Can I rate-limit functions_complete_error? +

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

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

functions_complete_error 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.