create_function

THE RISK

Medium Risk

Why create_function needs a policy

The name 'create_function' strongly implies creating a new resource (e.g., a Lambda function or similar cloud function), which is a Write operation. However, with no description available, the exact behavior is unknown — it could potentially be Execute or even Destructive if it triggers deployments or overwrites existing resources. Confidence is lowered due to the empty description.

From the tool's definition Tool name: create_function — description is empty/uninformative

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

POLICY

How to control create_function

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

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "create_function": {
      "limits": [
        {
          "counter": "create_function_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

create_function 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.

Create a free account and register Amazon EKS 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.

LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

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Go deeper

Govern customer-ops agents → PII redaction, approval on external messages, and no-bulk-delete rules on the records agents change.
The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Argument validation → Checking tool call arguments against schema and policy before they run.
Scoped token → Per-person credentials that grant a defined subset of servers and tools.
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 create_function

What does the create_function tool do? +

create_function. It is categorised as a Write tool in the Amazon EKS MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on create_function? +

Register the Amazon EKS MCP Server MCP server in PolicyLayer and add a rule for create_function: 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 Amazon EKS MCP Server. Nothing to install.

What risk level is create_function? +

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

Can I rate-limit create_function? +

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

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

create_function is provided by the Amazon EKS MCP Server MCP server (awslabs.eks-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 Amazon EKS MCP Server tool call.

Start from Amazon EKS 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 →