update_chapter · Narrarium MCP: Risk & Policy

WHAT IT DOES

What update_chapter does on Narrarium

AI agents use update_chapter 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_chapter needs a policy

This tool creates or modifies data reversibly within the book repository system. It updates chapter metadata (summary, POV, tags) and notes, which are changes that can be undone or reverted. The tool is explicitly constrained to avoid 'touching chapter numbering or folder naming,' reducing risk.

From the tool's definition Tool description states 'Update an existing chapter metadata file and optional chapter notes body' - uses 'Update' verb indicating modification of existing data. Explicitly scoped to 'metadata' and 'notes' rather than destructive operations.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

update_chapter Rate-limited

update_chapter 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_chapter": {
      "limits": [
        {
          "counter": "update_chapter_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_chapter

What does the update_chapter tool do? +

Update an existing chapter metadata file and optional chapter notes body. Use this for summary, POV, tags, and chapter notes changes without touching chapter numbering or folder naming. In prose bodies, keep canon names as plain text instead of markdown links. 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_chapter? +

Register the Narrarium MCP server in PolicyLayer and add a rule for update_chapter: 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_chapter? +

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

Can I rate-limit update_chapter? +

Yes. Add a rate_limit block to the update_chapter 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_chapter completely? +

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

update_chapter 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.