AI agents invoke data_merge to trigger actions in InDesign UXP MCP Server. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.
A data merge operation reads data from an external source and programmatically populates document fields/templates, constituting an execution of a multi-step workflow that modifies document content. It goes beyond a simple write because it orchestrates external data ingestion and transformation.
From the tool's definition "Perform data merge operation" — triggers an external operation (data merge) that processes and applies external data sources to modify document content
Documented attack patterns abuse exactly the kind of access data_merge gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and InDesign UXP MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for data_merge:
{
"version": "1",
"default": "deny",
"tools": {
"data_merge": {
"limits": [
{
"counter": "data_merge_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}data_merge stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.
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Perform data merge operation. It is categorised as a Execute tool in the InDesign UXP MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the InDesign UXP MCP Server MCP server in PolicyLayer and add a rule for data_merge: 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 InDesign UXP MCP Server. Nothing to install.
data_merge is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the data_merge 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 data_merge. 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.
data_merge is provided by the InDesign UXP MCP Server MCP server (theloniuser/indesign-uxp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 135 InDesign UXP MCP Server tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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135 InDesign UXP MCP Server tools catalogued and risk-classified — across an index of 42,500+ MCP servers.