Update a named color slot in the document theme.
AI agents use set_theme_color 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.
The tool modifies document theme colors, which is a write operation that changes document state but is reversible (colors can be changed again). It does not delete data, execute arbitrary code, or cause financial impact. The blast radius is medium because theme changes could affect document appearance across multiple sections, but such changes are not destructive and can be undone.
From the tool's definition Tool description states 'Update a named color slot in the document theme' — this is a modification operation that changes document properties reversibly.
Documented attack patterns abuse exactly the kind of access set_theme_color 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_theme_color:
{
"version": "1",
"default": "deny",
"tools": {
"set_theme_color": {
"limits": [
{
"counter": "set_theme_color_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}set_theme_color 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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Update a named color slot in the document theme. 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_theme_color: 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_theme_color 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_theme_color 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_theme_color. 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_theme_color 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.