AI agents invoke data_merge to trigger actions in Indesign. 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 executes a batch publishing workflow: it reads an external data source, merges it with a document template, and produces one or more output documents. This is a triggered external operation with side effects (file creation, document modification) that depends on arguments, placing it in Execute. Severity is high because a misconfigured merge could overwrite or mass-produce incorrect documents.
From the tool's definition "Perform data merge operation" — triggers an InDesign data merge workflow that combines a data source with a document template to generate output
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, 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 MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Indesign 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. 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 MCP server (lucdesign/indesign-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Indesign, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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36 Indesign tools catalogued and risk-classified — across an index of 43,000+ MCP servers.