FastBill

Use this skill for FastBill invoices, customers, payments, reminders, and document metadata. The helper wraps concrete FastBill API services: it serializes JSON-shaped inputs to XML and parses XML responses.

Core Rules

• Use the helper plus built-in http_request for live API calls. Do not use curl, ad hoc node -e, grep, or shell parsing for FastBill.
• FastBill API URL: https://my.fastbill.com/api/1.0/api.php. The /api/1.0/ prefix is only for secret-route matching.
• Basic auth is injected by the gateway from FASTBILL_BASIC_AUTH. Never print, build, or ask for the FastBill API key.
• Writes require explicit operator intent and --operator-grant. Prefer --dry-run when converting free text, CSV, or time tracking into invoice data.
• Prefer invoice IDs for writes. If multiple invoices/customers match, ask for the exact ID before writing.
• If unsure about a service or field, check https://apidocs.fastbill.com.

Commands

Show commands:

node skills/fastbill/fastbill.cjs --help

Build an http_request payload for the built-in http_request tool:

node skills/fastbill/fastbill.cjs http-request invoice.get --filter-json '{"INVOICE_ID":"123"}'
node skills/fastbill/fastbill.cjs http-request customer.create --data-json '{"CUSTOMER_TYPE":"business","ORGANIZATION":"Acme GmbH","COUNTRY_CODE":"DE"}' --operator-grant

Parse a saved http_request response wrapper/body:

node skills/fastbill/fastbill.cjs parse-response --body-file /tmp/fastbill-response.json

Direct helper network calls are only for operator-controlled shell tests with a valid gateway token already exported:

node skills/fastbill/fastbill.cjs request invoice.get --filter-json '{"INVOICE_ID":"123"}'

Common invoice payloads:

node skills/fastbill/fastbill.cjs http-request invoice.get --filter-json '{"END_DUE_DATE":"2026-04-08"}' --limit 100
node skills/fastbill/fastbill.cjs http-request invoice.create --data-json '{"CUSTOMER_ID":"123","INVOICE_TITLE":"Consulting Januar - Juni 2026","ITEMS":{"ITEM":[{"DESCRIPTION":"Consulting","QUANTITY":"8","UNIT_PRICE":"120.00","VAT_PERCENT":"19"}]}}' --operator-grant
node skills/fastbill/fastbill.cjs http-request invoice.update --data-json '{"INVOICE_ID":"456","INVOICE_TITLE":"YouGov SVOD Januar - Juni 2026"}' --operator-grant
node skills/fastbill/fastbill.cjs http-request invoice.setpaid --data-json '{"INVOICE_ID":"456","PAID_DATE":"2026-05-07","PAYMENT_METHOD":"bank transfer"}' --operator-grant
node skills/fastbill/fastbill.cjs http-request invoice.sendbyemail --data-json '{"INVOICE_ID":"456","RECIPIENT":{"TO":"billing@example.com"},"SUBJECT":"Payment reminder","MESSAGE":"Please review the outstanding invoice and payment status."}' --operator-grant

Clone / Copy Invoice

FastBill's API does not expose a dedicated invoice clone/copy service, even though the UI has one. Implement clone as invoice.get then invoice.create.

1. Use one targeted invoice.get; prefer date, customer/project text, title, and service-period terms over broad account-wide searches.
2. Select one source invoice. If ambiguous, ask for the invoice ID.
3. Copy relevant source fields: CUSTOMER_ID, CUSTOMER_COSTCENTER_ID, CONTACT_ID, CURRENCY_CODE, TEMPLATE_ID/TEMPLATE_HASH, INTROTEXT, INVOICE_TITLE, references, discounts, VAT settings, and ITEMS.
4. Omit lifecycle/source fields: INVOICE_ID, INVOICE_NUMBER, STATE, PAID_DATE, PAYMENTS, DOCUMENT_URL, DETAILS_URL, totals, and cancellation flags.
5. Apply requested changes, then create the draft with invoice.create --operator-grant. Extra reads need a concrete missing field.

Invoice Title Fields

• Invoice title field: INVOICE_TITLE in invoice.create and invoice.update. Do not use TITLE, NAME, or SUBJECT.
• Existing draft title edit: invoice.update with INVOICE_ID and INVOICE_TITLE.
• INTROTEXT is intro/body text before line items.
• ITEMS.ITEM[].DESCRIPTION is line-item text.
• SUBJECT is only for email actions such as invoice.sendbyemail.
• Do not set INVOICE_NUMBER when creating or editing a draft title.

Write Services

These require --operator-grant: customer.create/update/delete, contact.create/update/delete, invoice.create/update/delete/complete/cancel/lock/sendbyemail/sendbypost/setpaid, estimate.create/delete/sendbyemail/createinvoice, article.create/update/delete, recurring.create/update/delete, revenue.create/setpaid/delete, expense.create, project.create/update/delete, time.create/update/delete, and document.create, webhook.create/delete.

Errors

• Gateway 401 mentioning WEB_API_TOKEN or GATEWAY_API_TOKEN: the request did not reach FastBill; use built-in http_request in normal runtime.
• Missing/forbidden secret route: fix FASTBILL_BASIC_AUTH or its route.
• FastBill 401 with Wrong API KEY / credentials: the route worked, but FastBill rejected the stored Basic credential.

References

• Operator setup and API notes: references/operator-setup.md

Validation

Run:

python3 skills/skill-creator/scripts/quick_validate.py skills/fastbill
node skills/fastbill/fastbill.cjs --help
node skills/fastbill/fastbill.cjs http-request invoice.get --filter-json '{"INVOICE_ID":"123"}'
node skills/fastbill/fastbill.cjs request invoice.get --filter-json '{"INVOICE_ID":"123"}' --dry-run