tunable_update

Update an existing tunable by its ID. Use tunable_list to find the ID. All fields are optional — only provide the ones to change.

SERVERNasbridge SOURCEmaverick0628/nasbridge

Medium RISK CLASS

Category Write

Parameters 00 required

Recommended Rate-limitedsee the rule below

Registry record Grade F, identity unverified Pull the record →

This record as markdown: /tools/nasbridge/tunable-update.md

WHAT IT DOES

What tunable_update does on Nasbridge

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

RISK

Why tunable_update is rated Medium

This tool modifies system tunables (kernel/runtime parameters) on a TrueNAS SCALE instance. While it is a reversible write operation (values can be changed back), modifying system tunables can have significant system-wide impact, potentially destabilizing the system or causing service outages if incorrect values are applied. The severity is high due to the blast radius of misconfigured kernel or system parameters.

From the tool's definition Update an existing tunable by its ID. All fields are optional — only provide the ones to change.

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs tunable_update safely

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

tunable_update Rate-limited

tunable_update 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": {
    "tunable_update": {
      "limits": [
        {
          "counter": "tunable_update_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL → Instant setup, no code required.

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

FAQ

Questions about tunable_update

What does the tunable_update tool do? +

Update an existing tunable by its ID. Use tunable_list to find the ID. All fields are optional — only provide the ones to change. It is categorised as a Write tool in the Nasbridge MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on tunable_update? +

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

What risk level is tunable_update? +

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

Can I rate-limit tunable_update? +

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

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

tunable_update is provided by the Nasbridge MCP server (maverick0628/nasbridge). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

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