update_instance · Ns Hpc MCP: Risk & Policy

WHAT IT DOES

What update_instance does on Ns Hpc

AI agents use update_instance to create or update resources in Ns Hpc — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Ns Hpc environment.

WHY IT NEEDS A POLICY

Why update_instance needs a policy

This tool performs a reversible modification of instance metadata (description field). It is a Write operation because it creates or modifies data without deletion or irreversible consequences. Severity is low because metadata updates have minimal blast radius and do not affect running computations, financial systems, or data integrity.

From the tool's definition Tool description states 'Update or get an instance's metadata (currently only description)'. The 'update' operation is reversible and modifies only instance metadata, not core functionality or data integrity.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

update_instance Rate-limited

update_instance 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.

View as policy code

policy.json

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

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Ns Hpc, so you can run agents against it safely.

FAQ

Questions about update_instance

What does the update_instance tool do? +

Update or get an instance's metadata (currently only description). It is categorised as a Write tool in the Ns Hpc MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on update_instance? +

Register the Ns Hpc MCP server in PolicyLayer and add a rule for update_instance: 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 Ns Hpc. Nothing to install.

What risk level is update_instance? +

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

Can I rate-limit update_instance? +

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

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

update_instance is provided by the Ns Hpc MCP server (li-yq/namespaced-hpc-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.