This record as markdown: /tools/io-github-2s-io-mcp/queue.enqueue.md
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 queue.enqueue is rated Medium
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
The rule that runs queue.enqueue safely
PolicyLayer is an MCP gateway: it sits between your AI agents and Mcp, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For queue.enqueue, this is the rule to start with:
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.
The button opens the PolicyLayer dashboard: create your workspace, connect Mcp, apply this rule, and every queue.enqueue call is checked against it from then on.
Questions about queue.enqueue
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.
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.
queue.enqueue is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
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.
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.
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.
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