Mark all fields as dirty so Word recalculates on open.
AI agents use update_fields to create or update resources in Docx — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Docx environment.
This tool modifies the state of fields within a Word document by flagging them for recalculation. It is a reversible write operation that changes document metadata/state rather than deleting data or executing arbitrary code. The blast radius is medium since it affects the entire document's fields, but it doesn't irreversibly destroy data.
From the tool's definition Mark all fields as dirty so Word recalculates on open
Documented attack patterns abuse exactly the kind of access update_fields gives an agent:
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 update_fields:
{
"version": "1",
"default": "deny",
"tools": {
"update_fields": {
"limits": [
{
"counter": "update_fields_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}update_fields 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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Mark all fields as dirty so Word recalculates on open. 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.
Register the Docx MCP server in PolicyLayer and add a rule for update_fields: 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.
update_fields 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 update_fields 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 update_fields. 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.
update_fields 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.
Start from Docx, 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.
219 Docx tools catalogued and risk-classified — across an index of 43,000+ MCP servers.