AI agents use unmerge_cells to create or update resources in Office Editor — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Office Editor environment.
Unmerging cells in Excel is a reversible write operation that modifies document structure and formatting but does not delete data or execute arbitrary code. The tool transforms the spreadsheet layout rather than destroying information. This is consistent with other Write-category tools on the server that modify Office documents.
From the tool's definition Tool name 'unmerge_cells' indicates modification of cell formatting in Excel documents. The sibling tools (add_animation, add_conditional_formatting, add_data_bar, add_header_footer, add_slide, add_text_box, etc.) are all document creation/modification…
Documented attack patterns abuse exactly the kind of access unmerge_cells gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Office Editor, and nothing reaches the server without passing your rules. This is the rule we recommend for unmerge_cells:
{
"version": "1",
"default": "deny",
"tools": {
"unmerge_cells": {
"limits": [
{
"counter": "unmerge_cells_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}unmerge_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.
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unmerge_cells. It is categorised as a Write tool in the Office Editor MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Office Editor MCP server in PolicyLayer and add a rule for unmerge_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 Office Editor. Nothing to install.
unmerge_cells is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the unmerge_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.
Set action: deny in the PolicyLayer policy for unmerge_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.
unmerge_cells is provided by the Office Editor MCP server (thewdy/office-editor-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 88 Office Editor tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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88 Office Editor tools catalogued and risk-classified — across an index of 42,500+ MCP servers.