queue.enqueue · MCP: Risk & Policy

WHAT IT DOES

What queue.enqueue does on Mcp

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

WHY IT NEEDS A POLICY

Why queue.enqueue needs a policy

This tool writes a new message into a queue, which is a reversible write operation (messages can typically be dequeued or removed). The financial context of the server (USDC payments) adds some concern, but the tool itself does not directly move money — it enqueues a message. Severity is medium because misuse could flood queues or enqueue malicious payloads, and each call incurs a pay-per-call cost on the server.

From the tool's definition 'append a message to a durable, wallet-scoped queue' — creates/writes data reversibly to a queue

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

queue.enqueue Rate-limited

queue.enqueue 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": {
    "queue.enqueue": {
      "limits": [
        {
          "counter": "queue.enqueue_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 Mcp, so you can run agents against it safely.

FAQ

Questions about queue.enqueue

What does the queue.enqueue tool do? +

QUEUE: append a message to a durable, wallet-scoped queue. It is categorised as a Write tool in the Mcp MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on queue.enqueue? +

Register the MCP server in PolicyLayer and add a rule for queue.enqueue: 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 Mcp. Nothing to install.

What risk level is queue.enqueue? +

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

Can I rate-limit queue.enqueue? +

Yes. Add a rate_limit block to the queue.enqueue 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 queue.enqueue completely? +

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

queue.enqueue is provided by the MCP server (@2sio/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.