create_notebook · Marimo MCP: Risk & Policy

WHAT IT DOES

What create_notebook does on Marimo

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

WHY IT NEEDS A POLICY

Why create_notebook needs a policy

This tool creates a new file artifact (a marimo notebook) which is a reversible write operation. It does not execute code, delete data, or move money. While file creation could theoretically be destructive if it overwrites an existing file at the same path, the description specifies creating 'a new' notebook, suggesting normal creation semantics.

From the tool's definition Tool description states 'Create a new marimo notebook at the given absolute path.' The verb 'Create' indicates data creation, and a notebook file is a persistent data artifact.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

create_notebook Rate-limited

create_notebook 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": {
    "create_notebook": {
      "limits": [
        {
          "counter": "create_notebook_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 Marimo, so you can run agents against it safely.

FAQ

Questions about create_notebook

What does the create_notebook tool do? +

Create a new marimo notebook at the given absolute path. It is categorised as a Write tool in the Marimo MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on create_notebook? +

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

What risk level is create_notebook? +

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

Can I rate-limit create_notebook? +

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

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

create_notebook is provided by the Marimo MCP server (vladisluv12/marimo-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.