notebook_read_cell_output

THE RISK

Low Risk

Why notebook_read_cell_output needs a policy

This tool retrieves and queries data (cell outputs) from an existing notebook without modifying, executing, or deleting anything. It is a straightforward read operation that presents no risk of unintended modifications or destructive actions.

From the tool's definition Tool name 'notebook_read_cell_output' and description 'Reads the output list of a specific code cell' indicate a retrieval operation with no side effects.

Documented attack patterns abuse exactly the kind of access notebook_read_cell_output gives an agent:

POLICY

How to control notebook_read_cell_output

PolicyLayer is an MCP gateway — it sits between your AI agents and Claude Code Notebook MCP, and nothing reaches the server without passing your rules. This is the rule we recommend for notebook_read_cell_output:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "notebook_read_cell_output": {}
  }
}

notebook_read_cell_output is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.

Create a free account and register Claude Code Notebook MCP — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

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EXPLORE

Related tools and policies

More Claude Code Notebook MCP tools

Destructive notebook_delete Deletes an existing notebook file Destructive notebook_delete_cell Deletes a specific cell Write notebook_clear_all_outputs Clears outputs and execution counts for all code cells Write notebook_clear_cell_outputs Clears the outputs and execution count of a specific cell Write notebook_add_cell Adds a new code or markdown cell after a specified index Write notebook_bulk_add_cells Adds multiple cells to a notebook in a single operation Write notebook_change_cell_type Changes a cell Write notebook_create Creates a new, empty notebook file

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Data exfiltration → How read access becomes an exfiltration channel when chained with untrusted content.
MCP token cost → What connecting this server costs in context-window tokens on every request.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about notebook_read_cell_output

What does the notebook_read_cell_output tool do? +

Reads the output list of a specific code cell. It is categorised as a Read tool in the Claude Code Notebook MCP MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on notebook_read_cell_output? +

Register the Claude Code Notebook MCP server in PolicyLayer and add a rule for notebook_read_cell_output: 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 Claude Code Notebook MCP. Nothing to install.

What risk level is notebook_read_cell_output? +

notebook_read_cell_output is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit notebook_read_cell_output? +

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

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

notebook_read_cell_output is provided by the Claude Code Notebook MCP server (mstampfer/claude-code-notebook-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Claude Code Notebook MCP tool call.

Start from Claude Code Notebook MCP, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

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