update_script · Narrarium MCP: Risk & Policy

WHAT IT DOES

What update_script does on Narrarium

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

WHY IT NEEDS A POLICY

Why update_script needs a policy

This tool modifies existing content in a structured, versioned repository (book/writing project). Changes are reversible—prior versions can be restored and edits can be undone. It does not delete content (would be Destructive) or execute arbitrary code (would be Execute). The scope is limited to updating scene scripts and metadata within a local Narrarium repository.

From the tool's definition Tool description states "Update an existing scene script" and "refine beats, add new lines, or patch frontmatter". These are reversible modifications to existing data (scripts/<chapter>/<paragraph>.md).

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

update_script Rate-limited

update_script 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_script": {
      "limits": [
        {
          "counter": "update_script_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 Narrarium, so you can run agents against it safely.

FAQ

Questions about update_script

What does the update_script tool do? +

Update an existing scene script in scripts/<chapter>/<paragraph>.md. Use this to refine beats, add new lines, or patch frontmatter (e.g. change location or tags). Provide \. It is categorised as a Write tool in the Narrarium 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_script? +

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

What risk level is update_script? +

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

Can I rate-limit update_script? +

Yes. Add a rate_limit block to the update_script 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_script completely? +

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

update_script is provided by the Narrarium MCP server (narrarium-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.