Replace a DOCX part with new XML. Validates well-formedness first.
AI agents use write_part 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 data reversibly by replacing XML parts within a Word document. While replacement could theoretically be undone (e.g., via undo or restoration), the tool itself performs a Write operation—it does not delete irreversibly (Destructive), execute arbitrary code (Execute), or move money (Financial).
From the tool's definition Tool description states 'Replace a DOCX part with new XML', which is a direct modification operation. The verb 'Replace' indicates the tool overwrites/modifies document content at the OOXML structural level.
Documented attack patterns abuse exactly the kind of access write_part 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 write_part:
{
"version": "1",
"default": "deny",
"tools": {
"write_part": {
"limits": [
{
"counter": "write_part_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}write_part 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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Replace a DOCX part with new XML. Validates well-formedness first. 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 write_part: 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.
write_part 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 write_part 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 write_part. 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.
write_part 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.