n8n-nodes-coretool

This is an n8n community node. It lets you use the Coretool E-Invoice API (https://coretool.de) in your n8n workflows.

Coretool creates and validates German/EU e-invoices: ZUGFeRD 2.x (PDF with embedded XML) and XRechnung (CII or UBL XML), checks Leitweg-IDs for invoices to public authorities and reports the remaining quota of your API key.

n8n is a fair-code licensed workflow automation platform.

Installation Operations Credentials Compatibility Usage Resources

Installation

Follow the installation guide in the n8n community nodes documentation.

Package name: n8n-nodes-coretool

Operations

| Operation | What it does | Costs a call? | | --- | --- | --- | | Create an E-Invoice | Builds a ZUGFeRD PDF or XRechnung XML from invoice data (seller, buyer, line items, payment) and returns it as a binary file plus the calculated totals. | yes | | Validate an E-Invoice | Uploads a PDF or XML (max. 5 MB) and validates it with the official KoSIT validator. Optionally returns the full report. | yes | | Check a Leitweg-ID | Checks the syntax and check digit of a German Leitweg-ID. An invalid ID is a normal result (valid: false), not a failure. | yes (empty input is free) | | Get Usage | Returns the plan and remaining calls of the API key. | no |

Create an E-Invoice – fields

• Format: zugferd (PDF), xrechnung_cii or xrechnung_ubl (XML)
• Invoice Number, Invoice Date, Delivery Date (only the date part is used)
• Seller / Buyer: name, street, ZIP code, city, country (default DE), tax number (seller), VAT ID, email, phone
• Line Items: enter them as fields or paste a JSON array (description, quantity, unit, unit_price, tax_rate)
• Payment: IBAN (required), BIC, bank name, due in days (max. 365) or due date, terms
• Additional Fields: currency, Leitweg-ID, buyer reference, order reference, notes, tax exemption (small business § 19 UStG, reverse charge, intra-community supply, § 4 UStG, rental), PDF template (classic, modern, dezent, clean), accent colour and logo (PDF only)

The created file is written to the binary field you choose (default data). The JSON output contains filename, mime_type, net_total, tax_total, gross_total, amount_due, totals, validation and usage.

Credentials

1. Sign in at https://coretool.de and create an API key (menu API keys). Keys start with ct_live_.
2. In n8n create a Coretool API credential and paste the key. The credential test calls GET /v1/auth/test, which does not cost a call.

For trying out the node you can also create a test key (ct_test_…) in your account, see https://coretool.de/e-rechnung-api#testmodus. New keys include a few free calls; see https://coretool.de/e-rechnung-api#kontingent for plans.

Compatibility

Built and tested with n8n 2.x (last manual test: n8n 2.44.4, Node.js 22). The node uses only n8n's built-in HTTP helpers and has no runtime dependencies.

Usage

Example workflows are included in the examples folder of the repository – import them via Workflows → Import from file:

• create-e-invoice-from-webhook.json – Webhook receives invoice data → Create an E-Invoice → send the PDF by e-mail
• validate-e-invoice-file.json – Read a file from disk → Validate an E-Invoice → IF valid
• check-leitweg-id.json – Manual trigger → Check a Leitweg-ID

Quick start without importing:

1. Add a Manual Trigger and a Coretool node, select your Coretool API credential.
2. Choose Get Usage and click Execute workflow – the output shows your plan and remaining calls.
3. Switch to Check a Leitweg-ID and enter e.g. 04011000-1234512345-06 – the output contains valid: true.
4. Switch to Create an E-Invoice, fill in seller, buyer, one line item and the IBAN – the output contains the e-invoice as binary file data plus the totals.

Error handling

The node translates API responses into readable messages that tell you what to do:

• 401 – API key invalid or revoked: create a new key at coretool.de and update the credential
• 402 – no calls left (free calls used up or plan limit reached)
• 413 – file larger than 5 MB
• 429 – too many requests: the message contains the seconds to wait
• 503 – validation service briefly unavailable: try again in a minute
• 400 – missing or invalid invoice data: the description lists the affected fields

Enable Continue On Fail on the node to receive these messages in the error field of the output item instead of stopping the workflow.

Resources

• n8n community nodes documentation
• Coretool E-Invoice API
• Support: [email protected]

Development

npm ci
npm run lint
npm run build
CORETOOL_TEST_KEY=ct_test_... npm test   # runs the API tests against api.coretool.de (use a test key)

Without CORETOOL_TEST_KEY the tests are skipped. By default the tests load a small stub instead of the n8n-workflow package; set CORETOOL_REAL_N8N_WORKFLOW=1 to run them against the installed n8n-workflow.

Releases are published to npm exclusively by the GitHub Actions workflow .github/workflows/publish.yml (npm trusted publishing with provenance), triggered by a version tag.

License

MIT – © 2026 Coretool (Tim Tüchsen)

Notes from the API tests (2026-10-20)

• A Leitweg-ID is only accepted for the XRechnung formats (xrechnung_cii, xrechnung_ubl), not for ZUGFeRD.
• XRechnung requires a seller phone number (seller.phone, rule BR-DE-6); the API returns a clear 400 error otherwise.