open_register · FacturaHub MCP Server MCP: Risk & Policy

WHAT IT DOES

What open_register does on FacturaHub MCP Server

AI agents use open_register to create or update resources in FacturaHub MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your FacturaHub MCP Server environment.

WHY IT NEEDS A POLICY

Why open_register needs a policy

This tool creates a new cash register session, which is a write operation that modifies the state of the POS system by establishing a new financial tracking record. While it involves money-related operations, it is not a Financial category tool because it doesn't move money or commit financial obligations—it merely opens a session to track cash.

From the tool's definition Tool description states 'Open a new cash register session with initial cash amount,' which creates a new financial record (cash register session) with an initial state. This is a reversible write operation (the session can be closed or adjusted).

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

open_register Rate-limited

open_register 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.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "open_register": {
      "limits": [
        {
          "counter": "open_register_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches FacturaHub MCP Server, so you can run agents against it safely.

FAQ

Questions about open_register

What does the open_register tool do? +

[FacturaHub] Open a new cash register session with initial cash amount. It is categorised as a Write tool in the FacturaHub MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on open_register? +

Register the FacturaHub MCP Server MCP server in PolicyLayer and add a rule for open_register: 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 FacturaHub MCP Server. Nothing to install.

What risk level is open_register? +

open_register is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit open_register? +

Yes. Add a rate_limit block to the open_register 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.

How do I block open_register completely? +

Set action: deny in the PolicyLayer policy for open_register. 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.

What MCP server provides open_register? +

open_register is provided by the FacturaHub MCP Server MCP server (santy1422/facturahub-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.