list_pop_left

THE RISK

Critical Risk

Why list_pop_left needs a policy

Popping values from a list removes them permanently from the data store. This is a destructive operation because the data is consumed/deleted from the list and cannot be recovered without a separate backup. While it may seem like a minor operation, misuse by an AI agent could lead to unintended data loss from Redis or similar list-based storage.

From the tool's definition Pop value(s) from left of list — 'pop' removes elements from the data structure irreversibly

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 AWS, 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 AWS — 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 →

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EXPLORE

Related tools and policies

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All 300 AWS tools →

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Go deeper

Govern infrastructure agents → Production lockdown, region locks, and approval-to-delete on every infrastructure call agents make.
Critical-risk tools in AWS → 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 →
PolicyLayer vs alternatives → How deterministic, per-call MCP policy compares with gateways, identity layers, and authorisation platforms.

FAQ

Questions about list_pop_left

What does the list_pop_left tool do? +

Pop value(s) from left of list. Args: key: The name of the key count: Number of values to pop (optional) Returns: Value(s) or error message. It is categorised as a Destructive tool in the AWS 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 AWS 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 AWS. 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 AWS MCP server (@awslabs/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every AWS tool call.

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

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