AI agents use save_workbook to create or update resources in Ironcalc — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Ironcalc environment.
An AI agent can call save_workbook faster than any human can review — one bad instruction and it creates or modifies resources in Ironcalc by the hundred, each call as confident as the last.
Attacks that exploit this kind of access
Save the current workbook to an xlsx file. It is categorised as a Write tool in the Ironcalc MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Ironcalc MCP server in PolicyLayer and add a rule for save_workbook: 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 Ironcalc. Nothing to install.
save_workbook 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 save_workbook 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 save_workbook. 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.
save_workbook is provided by the Ironcalc MCP server (yolonir/ironcalc-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.