Manage customers, suppliers, articles, invoices, orders, offers, supplier invoices, vouchers, accounts, projects and payments in Fortnox, the Swedish cloud accounting and ERP platform.
Fortnox ships in the w6w first-party pack. It declares 54 actions, 2 health checks, and the host runs its code in a sandbox that never sees the credential.
io.w6w.fortnoxFortnox is the most widely used cloud accounting, invoicing and ERP platform for small and medium businesses in Sweden. This app covers Fortnox’s REST API v3 (api.fortnox.se) for the core accounting objects: customers, suppliers, articles, customer invoices (create, update, book, cancel, credit, email), orders, offers, supplier invoices, vouchers and voucher series, the chart of accounts, invoice payments, projects, cost centers, financial years and the connected company.
Every path, verb, query parameter, body field and enum was read on 2026-10-06 from Fortnox’s own OpenAPI 3.0.3 document (embedded in the Redoc page at api.fortnox.se/apidocs) and the developer guides at fortnox.se/developer, plus a live check of the Statuspage at status.fortnox.se.
Three details are easy to get wrong: bodies and responses are wrapped in a resource key ({"Customer": {...}}, lists as {"Customers": [...], "MetaInformation": {...}}); refresh tokens rotate, so every refresh invalidates the previous one; and OAuth scopes are per resource (customer, invoice, bookkeeping, …), each granting read and write, with access_type=offline required to receive a refresh token.
Three routes to the same 54 actions. The Workflow tab is generated from Fortnox's own manifest and carries its real ids, so it is copy-pasteable; the Code and CLI examples are the same call for any action on any app, so every app-specific value in them is a blank you fill in.
account-update Update a ledger account. Only the properties sent are changed; the number itself cannot be changed.
company-information-get Fetch the connected company: name, organisation number, address and database number.
customer-update Update a customer. Only the properties sent are changed; the rest are left as they are.
financial-year-list List the company's financial years; filter to the one containing a date.
invoice-create Create a customer invoice. Fortnox fills omitted fields from the company's predefined values.
invoice-credit Create a credit invoice for this invoice; it is referenced in CreditInvoiceReference.
invoice-list List customer invoices with Fortnox's own filters (status, dates, customer, project, OCR).
invoice-send-email Email the invoice to the customer. Fortnox exposes this as a GET that has a side effect.
invoice-update Update an unbooked invoice. Only the properties sent are changed; see the rows note.
me-get Fetch the Fortnox user the access token belongs to (needs the profile scope).
voucher-get Fetch one voucher by series and number. The same series and number repeat every year, so pass the financial year id.
A workflow step names the app and the action, and the editor fills in the
connection when you pick one. This is the Step shape from the
workflow spec, carrying Fortnox's real ids.
{
"manifestVersion": "2",
"name": "fortnox-example",
"steps": [
{
"id": "account-create",
"uses": {
"app": "io.w6w.fortnox",
"action": "account-create",
"connection": "conn_YOUR_CONNECTION_ID"
},
"with": {
"number": "<number>"
}
}
]
}account-create account-get account-list account-update article-create +49 more actions available
Every app-specific value here is a blank you have to fill in. An
app action is reached through the connection that authenticates it, so the
address is a connection id, not the app id — and connections belong to your account,
so a public page cannot know yours. Create one for Fortnox, then fill in
the three blanks: conn_YOUR_CONNECTION_ID, the action key, and the
parameters that action declares. The call itself is real — the shape is transcribed
from the studio's own snippet builder, which prints the same kind of blanks — but
nothing in it is specific to Fortnox. The Workflow tab is where this app's
real ids are.
npm install @w6w/sdkyarn add @w6w/sdkpnpm add @w6w/sdkdeno add npm:@w6w/sdkimport { W6wClient, isActionRun } from "@w6w/sdk";
// Reads W6W_BASE_URL and W6W_TOKEN from the environment when omitted.
const client = new W6wClient();
const envelope = await client.run({
urn: "conn_YOUR_CONNECTION_ID",
action: "account-create",
payload: {
number: "<value>",
// description: "<value>",
// active: "<value>",
// sru: "<value>",
// costCenterSettings: "<value>",
// projectSettings: "<value>",
// vatCode: "<value>",
// additionalFields: "<value>",
// financialYear: "<value>",
},
});
if (isActionRun(envelope)) console.log(envelope.value); npm install -g @w6w/cli w6w run conn_YOUR_CONNECTION_ID --action account-create --payload '{"number":"<value>"}' Give an AI agent Fortnox — without giving it Fortnox's credentials. One MCP endpoint exposes every app, function and workflow the caller is entitled to, as tools it can discover and run. Access is granted per team while we onboard.
One tool call{
"name": "w6w_invoke",
"arguments": {
"ref": "app:io.w6w.fortnox#account-create",
"input": {
"number": "<number>"
}
}
}
Every tool names its target with a single ref. The
app: form above doesn't name a connection at all — the
host resolves which of the caller's Fortnox connections to sign
with, and refuses rather than guesses when the answer is ambiguous.
The token is attached host-side, at the moment of the call. It is never a tool argument, never in the model's context, and never in a transcript — so a prompt injection has nothing to exfiltrate.
Tools are derived per end user from what that person has actually connected and is entitled to — not one shared bot identity carrying the union of everyone's access.
Multi-step work runs on the workflow engine and returns a run handle the agent can poll — retries, branching and state survive the conversation that started them.
Fortnox's declared health checks are on the surface too, so an agent can tell "the vendor is down" from "your credential expired" before it burns a retry on either.
The MCP surface is part of the hosted platform. Fortnox itself is MIT, and the runtime that executes it is source-available (FSL).
Fortnox declares its own checks, so its health is a property of the app rather than something the host guesses at.
Status of the `Fortnox API` and `Fortnox ID` (login) components on Fortnox's Atlassian Statuspage (status.fortnox.se). Other components on the page are unrelated to the API and are ignored.