send · Agent Bus MCP: Risk & Policy

WHAT IT DOES

What send does on Agent Bus

AI agents use send 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 send needs a policy

The tool sends a message to another agent without waiting for a response (fire-and-forget). This is a Write operation as it creates/posts a message on the shared message bus.

From the tool's definition Send a fire-and-forget message to another agent

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

send Rate-limited

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

FAQ

Questions about send

What does the send tool do? +

Send a fire-and-forget message to another agent. 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 send? +

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

What risk level is send? +

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

Can I rate-limit send? +

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

Set action: deny in the PolicyLayer policy for 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 send? +

send 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.