Reply to an existing comment (creates a threaded reply).
AI agents use reply_to_comment 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 creates new data (a reply/threaded comment) within a Word document. It modifies the document by adding content, but the modification is reversible (replies can be deleted or edited). This is a Write operation rather than Read (it creates, not just retrieves), Execute (it doesn't run arbitrary code), or Destructive (replies don't irreversibly delete data).
From the tool's definition Tool name 'reply_to_comment' and description 'Reply to an existing comment (creates a threaded reply)' indicates creation of new comment data within a document.
Documented attack patterns abuse exactly the kind of access reply_to_comment 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 reply_to_comment:
{
"version": "1",
"default": "deny",
"tools": {
"reply_to_comment": {
"limits": [
{
"counter": "reply_to_comment_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}reply_to_comment 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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Reply to an existing comment (creates a threaded reply). 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 reply_to_comment: 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.
reply_to_comment 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 reply_to_comment 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 reply_to_comment. 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.
reply_to_comment 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.
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219 Docx tools catalogued and risk-classified — across an index of 43,000+ MCP servers.