list_all_hosts

THE RISK

Low Risk

Why list_all_hosts needs a policy

This tool queries and returns a list of device names from the network inventory. It performs a read-only retrieval operation with no side effects, no code execution, no data modification, and no destructive capabilities. The minimal scope (device names only) and passive discovery nature confirm low severity.

From the tool's definition Tool name 'list_all_hosts' and description 'Return a minimal discovery list containing only the inventory device_name' indicates retrieval of inventory metadata with no modification or execution capability.

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

POLICY

How to control list_all_hosts

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

policy.json

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

list_all_hosts is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.

Create a free account and register Nornir 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.

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EXPLORE

Related tools and policies

More Nornir MCP Server tools

Execute traceroute Execute the traceroute command from the device to the specified destination. Execute send_command Send a validated read-only command or list of commands to the device. Read get_arp_table Get the device's ARP (Address Resolution Protocol) table. Read get_bgp_config Retrieve BGP configuration from the device. Read get_bgp_neighbors Get a summary of BGP (Border Gateway Protocol) neighbors. Read get_bgp_neighbors_detail Obtain a detailed view of all BGP neighbors. Read get_config Use NAPALM to retrieve device configurations (running, startup, or candidate). Read get_facts Retrieve high-level facts and information about the device (e.g., vendor, model, serial nu

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Data exfiltration → How read access becomes an exfiltration channel when chained with untrusted content.
MCP token cost → What connecting this server costs in context-window tokens on every request.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about list_all_hosts

What does the list_all_hosts tool do? +

Return a minimal discovery list containing only the inventory device_name. It is categorised as a Read tool in the Nornir MCP Server MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on list_all_hosts? +

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

What risk level is list_all_hosts? +

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

Can I rate-limit list_all_hosts? +

Yes. Add a rate_limit block to the list_all_hosts 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_all_hosts completely? +

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

list_all_hosts is provided by the Nornir MCP Server MCP server (yhvh-chen/nornir_mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Nornir MCP Server tool call.

Start from Nornir 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 →