queue.lease · MCP: Risk & Policy

WHAT IT DOES

What queue.lease does on Mcp

AI agents invoke queue.lease to trigger actions in Mcp. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

WHY IT NEEDS A POLICY

Why queue.lease needs a policy

Leasing from a queue is an Execute-level operation: it atomically modifies queue state by claiming items, which has side effects on the queue system. It is not purely a read (it changes ownership/state of queue items) and not destructive (items are not deleted). The description is truncated, lowering confidence.

From the tool's definition 'atomically claim up to' — suggests an atomic operation that claims/leases items from a queue, triggering an external state change

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

queue.lease Rate-limited

queue.lease stays usable, but rate-capped — a runaway agent can't fire it dozens of times 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.lease": {
      "limits": [
        {
          "counter": "queue.lease_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-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.lease

What does the queue.lease tool do? +

QUEUE: atomically claim up to. It is categorised as a Execute tool in the Mcp MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

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

Register the MCP server in PolicyLayer and add a rule for queue.lease: 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.lease? +

queue.lease is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit queue.lease? +

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

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

queue.lease 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.