Set formatting on a cell or range: font, size, color, alignment, background color, bold, italic
AI agents use numbers_format_cells to create or update resources in Iwork — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Iwork environment.
This tool modifies spreadsheet cell formatting (visual properties like font, color, alignment) reversibly without affecting underlying data, making it a Write operation. The blast radius is minimal—formatting changes can be undone and do not expose data, delete content, execute code, or create financial impact. Severity is low because misuse would only result in cosmetic spreadsheet changes.
From the tool's definition Tool name 'numbers_format_cells' and description 'Set formatting on a cell or range: font, size, color, alignment, background color, bold, italic' indicate modification of cell appearance properties in Numbers spreadsheets.
Documented attack patterns abuse exactly the kind of access numbers_format_cells gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Iwork, and nothing reaches the server without passing your rules. This is the rule we recommend for numbers_format_cells:
{
"version": "1",
"default": "deny",
"tools": {
"numbers_format_cells": {
"limits": [
{
"counter": "numbers_format_cells_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}numbers_format_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.
Free to start. No card required.
Set formatting on a cell or range: font, size, color, alignment, background color, bold, italic. It is categorised as a Write tool in the Iwork MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Iwork MCP server in PolicyLayer and add a rule for numbers_format_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 Iwork. Nothing to install.
numbers_format_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 numbers_format_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 numbers_format_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.
numbers_format_cells is provided by the Iwork MCP server (reichenbach/iwork_mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Iwork, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
114 Iwork tools catalogued and risk-classified — across an index of 43,000+ MCP servers.