ack · Agent Bus MCP: Risk & Policy

WHAT IT DOES

What ack does on Agent Bus

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

WHY IT NEEDS A POLICY

Why ack needs a policy

Acknowledging a message modifies the state of the message (marking it as processed/acknowledged) in the message bus. This is a reversible state change with minimal blast radius — it simply records that a message was handled. No data is deleted, no code is executed, and no financial operations occur.

From the tool's definition Acknowledge a message you successfully processed

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

ack Rate-limited

ack 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": {
    "ack": {
      "limits": [
        {
          "counter": "ack_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 Agent Bus, so you can run agents against it safely.

FAQ

Questions about ack

What does the ack tool do? +

Acknowledge a message you successfully processed (used with inbox claim_s). It is categorised as a Write tool in the Agent Bus MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on ack? +

Register the Agent Bus MCP server in PolicyLayer and add a rule for ack: 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 Agent Bus. Nothing to install.

What risk level is ack? +

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

Can I rate-limit ack? +

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

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

ack is provided by the Agent Bus MCP server (mustaphasteph/agent-bus). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.