AI agents use open_book to create or update resources in InDesign MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your InDesign MCP Server environment.
Opening a book in InDesign loads it into the application session, which creates a stateful change (an open document/book handle) and may trigger auto-processes. It is not purely read-only since it modifies application state, but it does not delete or irreversibly alter data. Write is the most appropriate category given the reversible state change.
From the tool's definition Open an existing InDesign book
Documented attack patterns abuse exactly the kind of access open_book gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and InDesign MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for open_book:
{
"version": "1",
"default": "deny",
"tools": {
"open_book": {
"limits": [
{
"counter": "open_book_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}open_book 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.
Free to start. No card required.
Open an existing InDesign book. It is categorised as a Write tool in the InDesign MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the InDesign MCP Server MCP server in PolicyLayer and add a rule for open_book: 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 MCP Server. Nothing to install.
open_book 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 open_book 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 open_book. 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.
open_book is provided by the InDesign MCP Server MCP server (zachshallbetter/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 MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
135 InDesign MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.