auto_fit_columns

THE RISK

Medium Risk

Why auto_fit_columns needs a policy

This tool modifies the formatting/layout of an Excel file by adjusting column widths. It's a reversible write operation (formatting change) with minimal blast radius — it doesn't delete data or execute arbitrary code.

From the tool's definition Automatically adjust column widths to fit content in Excel files

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

POLICY

How to control auto_fit_columns

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 auto_fit_columns:

policy.json

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

auto_fit_columns 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 auto_fit_columns

What does the auto_fit_columns tool do? +

Automatically adjust column widths to fit content in Excel files. 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 auto_fit_columns? +

Register the Excel MCP Server MCP server in PolicyLayer and add a rule for auto_fit_columns: 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 auto_fit_columns? +

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

Can I rate-limit auto_fit_columns? +

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

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

auto_fit_columns 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 →