create_invoice · Fortnox MCP: Risk & Policy

WHAT IT DOES

What create_invoice does on Fortnox

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

WHY IT NEEDS A POLICY

Why create_invoice needs a policy

This tool creates new invoices, which are reversible write operations (invoices can typically be modified or cancelled). It does not move money (Financial category) or delete data (Destructive category).

From the tool's definition Tool name 'create_invoice' and description 'Create a new invoice for a customer with line items' explicitly performs a create operation that generates new financial documents in Fortnox's accounting system.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

create_invoice Rate-limited

create_invoice 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": {
    "create_invoice": {
      "limits": [
        {
          "counter": "create_invoice_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

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Instant setup, no code required.

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

FAQ

Questions about create_invoice

What does the create_invoice tool do? +

Create a new invoice for a customer with line items. It is categorised as a Write tool in the Fortnox MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on create_invoice? +

Register the Fortnox MCP server in PolicyLayer and add a rule for create_invoice: 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 Fortnox. Nothing to install.

What risk level is create_invoice? +

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

Can I rate-limit create_invoice? +

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

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

create_invoice is provided by the Fortnox MCP server (proviscale/fortnox-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.