add_sheet

THE RISK

Medium Risk

Why add_sheet needs a policy

This tool creates a new sheet, which is a reversible write operation. It modifies the file structure by adding a new worksheet but does not delete or overwrite existing data, nor does it execute arbitrary code or trigger financial transactions. The severity is medium because uncontrolled sheet addition could clutter files or consume resources, but the operation is easily undone by removing the sheet.

From the tool's definition Tool name 'add_sheet' and description 'Add a new sheet to an existing Excel file' indicate creation of new data structures within a spreadsheet.

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

POLICY

How to control add_sheet

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

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "add_sheet": {
      "limits": [
        {
          "counter": "add_sheet_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

add_sheet 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.

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

LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Argument validation → Checking tool call arguments against schema and policy before they run.
Scoped token → Per-person credentials that grant a defined subset of servers and tools.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about add_sheet

What does the add_sheet tool do? +

Add a new sheet to an existing Excel file. It is categorised as a Write tool in the Excel MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on add_sheet? +

Register the Excel MCP Server MCP server in PolicyLayer and add a rule for add_sheet: 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 Excel MCP Server. Nothing to install.

What risk level is add_sheet? +

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

Can I rate-limit add_sheet? +

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

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

add_sheet is provided by the Excel MCP Server MCP server (ishayoyo/excel-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Excel MCP Server tool call.

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

CHECK YOUR STACK →