merge_cells

THE RISK

Medium Risk

Why merge_cells needs a policy

The tool modifies table structure by merging cells, which changes the document layout and cell properties. This is a Write operation because it alters document content reversibly (merges can be undone). It does not delete data irreversibly (not Destructive), does not execute arbitrary code (not Execute), does not read-only (not Read), and does not involve financial operations (not Financial).

From the tool's definition Merge a rectangular range of cells. Horizontal: gridSpan. Vertical: vMerge. This modifies the table structure in the document by combining cells, which is a reversible data modification operation.

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

POLICY

How to control merge_cells

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

policy.json

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

merge_cells 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 Docx — 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

More Docx tools

Destructive delete_column_from_table Delete a column (0-based) from every row of a table. Destructive delete_comment Delete a comment and remove its range markers from the document. Destructive delete_content_control Remove an SDT content control wrapper, keeping its content in place. Destructive delete_custom_property Delete a custom document property by name. Destructive delete_endnote Delete an endnote and its in-body reference. Destructive delete_field Remove a complete complex field (begin through end runs) from the document. Destructive delete_footer Delete a footer by location: default, first, or even. Destructive delete_footnote Delete a footnote and its in-body reference.

All 219 Docx tools →

Write tools on other servers

M-Team MCP Server download_torrent YouTube MCP Server generate_video_title Android Forensics ADB MCP Server combine_reports 0xarchive web3_signup

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 merge_cells

What does the merge_cells tool do? +

Merge a rectangular range of cells. Horizontal: gridSpan. Vertical: vMerge. It is categorised as a Write tool in the Docx MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on merge_cells? +

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

What risk level is merge_cells? +

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

Can I rate-limit merge_cells? +

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

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

merge_cells is provided by the Docx MCP server (securityronin/docx-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Docx tool call.

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

CHECK YOUR STACK →