create_customer · Fortnox MCP: Risk & Policy

WHAT IT DOES

What create_customer does on Fortnox

AI agents use create_customer 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_customer needs a policy

This tool creates a new customer record in the accounting system, which is a reversible write operation. It does not delete data (thus not Destructive), execute arbitrary code (thus not Execute), move money (thus not Financial), or merely retrieve data (thus not Read).

From the tool's definition Tool name is 'create_customer' and description states 'Add a new customer to Fortnox.' The verb 'Add' and 'create' indicate data creation.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

create_customer Rate-limited

create_customer 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_customer": {
      "limits": [
        {
          "counter": "create_customer_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 Fortnox, so you can run agents against it safely.

FAQ

Questions about create_customer

What does the create_customer tool do? +

Add a new customer to Fortnox. 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_customer? +

Register the Fortnox MCP server in PolicyLayer and add a rule for create_customer: 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_customer? +

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

Can I rate-limit create_customer? +

Yes. Add a rate_limit block to the create_customer 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_customer completely? +

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

create_customer 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.