list_instances

List GCP Compute Engine instances

SERVERNcp SOURCE@portel/ncp

Low RISK CLASS

Category Read

Parameters 00 required

Recommended Allowedsee the rule below

Registry record Grade F, identity unverified Pull the record →

This record as markdown: /tools/io-github-portel-dev-ncp/list-instances.md

WHAT IT DOES

What list_instances does on Ncp

AI agents call list_instances to retrieve information from Ncp without modifying anything. It is typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.

RISK

Why list_instances is rated Low

This tool performs a read-only operation to enumerate GCP Compute Engine instances. It retrieves data about infrastructure without side effects, making it a Read category tool.

From the tool's definition 'List GCP Compute Engine instances' — a query operation that retrieves and displays information about existing compute resources without modifying or executing anything.

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs list_instances safely

PolicyLayer is an MCP gateway: it sits between your AI agents and Ncp, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For list_instances, this is the rule to start with:

list_instances Allowed

list_instances is read-only, so it stays allowed. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "list_instances": {}
  }
}

ALLOW ONLY THIS TOOL → Instant setup, no code required.

The button opens the PolicyLayer dashboard: create your workspace, connect Ncp, apply this rule, and every list_instances call is checked against it from then on.

FAQ

Questions about list_instances

What does the list_instances tool do? +

List GCP Compute Engine instances. It is categorised as a Read tool in the Ncp MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on list_instances? +

Register the Ncp MCP server in PolicyLayer and add a rule for list_instances: 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 Ncp. Nothing to install.

What risk level is list_instances? +

list_instances is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit list_instances? +

Yes. Add a rate_limit block to the list_instances 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_instances completely? +

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

list_instances is provided by the Ncp MCP server (@portel/ncp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

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