Write a value to a cell
AI agents use numbers_write_cell 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 data (a cell value) but does not irreversibly delete data, execute arbitrary code, move money, or trigger external operations. It is reversible—the value can be overwritten or undone.
From the tool's definition Tool name 'numbers_write_cell' and description 'Write a value to a cell' indicate the tool creates or modifies cell data in Numbers spreadsheets. The verb 'write' and context of operating on spreadsheet cells confirm reversible data modification.
Documented attack patterns abuse exactly the kind of access numbers_write_cell 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_write_cell:
{
"version": "1",
"default": "deny",
"tools": {
"numbers_write_cell": {
"limits": [
{
"counter": "numbers_write_cell_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}numbers_write_cell 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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Write a value to a cell. 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_write_cell: 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_write_cell 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_write_cell 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_write_cell. 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_write_cell 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.
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114 Iwork tools catalogued and risk-classified — across an index of 43,000+ MCP servers.