SDKs — SLK Invoices API

Four single-file clients with the same surface. No package manager, no dependencies: copy the file into your project. They live in the repository under integrations/sdk/.

Language	File	Requires	Style
Node.js	`node/slk-invoices.mjs` (+ `slk-invoices.d.ts`)	Node 18+	ESM, built-in `fetch`, JSDoc types
PHP	`php/SlkInvoices.php`	PHP 7.4+, cURL	class `SlkInvoices`, arrays in/out
Python	`python/slk_invoices.py`	Python 3.8+	`urllib`, snake_case
C#	`csharp/SlkInvoices.cs`	.NET 6+	`HttpClient`, `System.Text.Json`, `async`

Each folder has a README with install-by-copy and a ten-line example.

Surface#

Operation	Node	PHP	Python	C#	Endpoint
Issue (native shape)	`createDocument(id, doc)`	`createDocument($id, $doc)`	`create_document(id, doc)`	`CreateDocumentAsync(id, doc)`	`POST /create-document`
Issue (Invoice4U shape)	`createDocumentCompat(doc)`	`createDocumentCompat($doc)`	`create_document_compat(doc)`	`CreateDocumentCompatAsync(doc)`	`POST /create-document`
Search documents	`listDocuments(filters)`	`listDocuments($filters)`	`list_documents(**filters)`	`ListDocumentsAsync(...)`	`GET /documents`
One document	`getDocument(id)`	`getDocument($id)`	`get_document(id)`	`GetDocumentAsync(id)`	`GET /documents?id=`
Customers	`listCustomers(q)`, `createCustomer(c)`	same	`list_customers`, `create_customer`	`ListCustomersAsync`, `CreateCustomerAsync`	`GET`/`POST /customers`
Totals	`calculate(doc)`	`calculate($doc)`	`calculate(doc)`	`CalculateAsync(doc)`	`POST /calculate`
Verify a webhook	`verifyWebhook(raw, sig, secret)`	`SlkInvoices::verifyWebhook(...)`	`verify_webhook(...)`	`SlkInvoicesClient.VerifyWebhook(...)`	offline

Behaviour#

The base URL defaults to https://invoice.slk.co.il. Pass an origin, or the baseUrl a sandbox signup returns (…/api/billing/v1); both work.
The key is sent as X-Api-Key. createDocumentCompat sends it as token in the body instead, as the Invoice4U shape requires, and you pass just the doc object.
Every non-2xx answer raises an error carrying the HTTP status, the server's message (from error or d.ErrorMessage) and the parsed body: SlkInvoicesError (Node, Python), SlkInvoicesException (PHP, C#).
create-document is idempotent: re-calling with the same identifier returns the same document, so wrapping it in your own retry loop is safe. The SDKs do not retry by themselves.
Timeouts default to 30 seconds.
Money is integer agorot, quantities ×1000, VAT in basis points — the SDKs pass your data through untouched. See overview.
Python's list_documents takes from_ for the from filter, because from is a keyword.

verifyWebhook#

verifyWebhook(rawBody, signatureHeader, secret[, toleranceSeconds]) checks X-SLK-Signature (t=<unix>,v1=<hex>): HMAC-SHA256 of "<t>.<rawBody>" compared in constant time. It also rejects a timestamp more than 300 seconds off (pass 0 to skip that check, e.g. when replaying stored events). Always pass the raw body, before JSON parsing. See webhooks.

Testing#

The Node SDK and the signature algorithm are covered by test/sdk.test.ts, which also cross-checks the Python implementation against the server's own signer. The PHP and C# clients follow the same algorithm but are not exercised by the repository's test run; if you find a discrepancy, treat the OpenAPI document as the source of truth.

For other languages, generate a client from GET /api/billing/v1/openapi.json.