list_pop_left

THE RISK

Critical Risk

Why list_pop_left needs a policy

'Pop' is a destructive read operation that removes elements from a data structure irreversibly. The tool removes value(s) from the left end of a list, which is a non-reversible deletion of data. However, the description is sparse and it's unclear what data store this operates on (likely Redis or similar, given the context of a Prometheus/AWS server).

From the tool's definition Pop value(s) from left of list

Documented attack patterns abuse exactly the kind of access list_pop_left gives an agent:

POLICY

How to control list_pop_left

PolicyLayer is an MCP gateway — it sits between your AI agents and Prometheus MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for list_pop_left:

policy.json

{
  "version": "1",
  "default": "deny",
  "hide": [
    "list_pop_left"
  ]
}

list_pop_left disappears from the agent's tool list entirely, and any attempt to call it is denied. The rest of the server keeps working.

Create a free account and register Prometheus MCP Server — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

RESTRICT THIS TOOL →

Free to start. No card required.

EXPLORE

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All 805 Prometheus MCP Server tools →

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Go deeper

Critical-risk tools in Prometheus MCP Server → Every critical-risk tool this server exposes, in one view.
All critical-risk MCP tools → Every critical-risk tool across the catalogue, and the policy pattern that contains them.
The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Blast radius → How much damage one compromised or confused agent can do — and how to bound it.
Tool call approval → Approval gates on individual tool calls: auto-allow, prompt, or deny.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about list_pop_left

What does the list_pop_left tool do? +

Pop value(s) from left of list. It is categorised as a Destructive tool in the Prometheus MCP Server MCP Server, which means it can permanently delete or destroy data. Block by default and require explicit approval.

How do I enforce a policy on list_pop_left? +

Register the Prometheus MCP Server MCP server in PolicyLayer and add a rule for list_pop_left: 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 Prometheus MCP Server. Nothing to install.

What risk level is list_pop_left? +

list_pop_left is a Destructive tool with critical risk. Critical-risk tools should be blocked by default and only enabled with explicit human approval.

Can I rate-limit list_pop_left? +

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

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

list_pop_left is provided by the Prometheus MCP Server MCP server (awslabs.prometheus-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Prometheus MCP Server tool call.

Start from Prometheus MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →