Mark the first row as a repeating header row.
AI agents use set_header_row 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 or modifies document structure reversibly. While it changes the document, the modification is non-destructive and can be undone (the header status can be removed). It does not execute arbitrary code, delete data, or create financial obligations. The moderate severity reflects that misuse could corrupt document structure or cause rendering issues, but the change is recoverable.
From the tool's definition "Mark the first row as a repeating header row" — this modifies document structure by designating a table row's property (header status), which affects document formatting and rendering but is reversible.
Documented attack patterns abuse exactly the kind of access set_header_row 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 set_header_row:
{
"version": "1",
"default": "deny",
"tools": {
"set_header_row": {
"limits": [
{
"counter": "set_header_row_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}set_header_row 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 the first row as a repeating header row. 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 set_header_row: 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.
set_header_row 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 set_header_row 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 set_header_row. 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.
set_header_row 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.