register_expense · FacturaHub MCP Server MCP: Risk & Policy

WHAT IT DOES

What register_expense does on FacturaHub MCP Server

AI agents use register_expense 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 register_expense needs a policy

This tool creates/records a new expense entry in the system, which is a reversible write operation — expenses can typically be edited or deleted if incorrect. While it affects financial calculations and VAT declarations, it does not move money, process payments, or commit financial obligations (Financial category). It is not destructive since expense records are not irreversibly deleted.

From the tool's definition Tool description states 'Register an expense' which creates a new expense record. It modifies financial data (adds expense entry) reversibly through a standard write operation, and handles VAT/tax calculations that affect accounting records.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

register_expense Rate-limited

register_expense 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": {
    "register_expense": {
      "limits": [
        {
          "counter": "register_expense_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 register_expense

What does the register_expense tool do? +

[FacturaHub] Register an expense with category and VAT/BTW rate. The taxRate is critical for quarterly VAT declarations — it calculates how much VAT you can recover. 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 register_expense? +

Register the FacturaHub MCP Server MCP server in PolicyLayer and add a rule for register_expense: 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 register_expense? +

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

Can I rate-limit register_expense? +

Yes. Add a rate_limit block to the register_expense 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 register_expense completely? +

Set action: deny in the PolicyLayer policy for register_expense. 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 register_expense? +

register_expense 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.