rental_add_unit · Excel Finance MCP: Risk & Policy

WHAT IT DOES

What rental_add_unit does on Excel Finance MCP

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

WHY IT NEEDS A POLICY

Why rental_add_unit needs a policy

This tool creates or adds a new entry (rental unit) to a property portfolio, which is a reversible write operation. While it affects financial records (rental properties), it does not move money (not Financial), execute arbitrary code (not Execute), or permanently delete data (not Destructive).

From the tool's definition Tool description states 'Add a rental unit to a property', indicating creation of a new record in a financial property management system.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

rental_add_unit Rate-limited

rental_add_unit 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": {
    "rental_add_unit": {
      "limits": [
        {
          "counter": "rental_add_unit_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 Excel Finance MCP, so you can run agents against it safely.

FAQ

Questions about rental_add_unit

What does the rental_add_unit tool do? +

Add a rental unit to a property. It is categorised as a Write tool in the Excel Finance MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on rental_add_unit? +

Register the Excel Finance MCP server in PolicyLayer and add a rule for rental_add_unit: 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 Excel Finance MCP. Nothing to install.

What risk level is rental_add_unit? +

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

Can I rate-limit rental_add_unit? +

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

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

rental_add_unit is provided by the Excel Finance MCP server (jeremycharlesgillespie/excel-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.