Businesses
List businesses, keep the slug, and use it on every later path.
A business slug is the tenant key. Get it from the API. Do not invent one from a name.
List, then use the slug
GET /v1/business/ returns businesses the token can access. Query parameters include page, page_size, and search (name, slug, and identifier). The operation is Businesses - List.
Each item in results has slug. Later paths are:
/v1/business/{business_slug}/...for the business, its accounts, documents, files, tags, contacts, periods, and reports/v1/invoicing/{business_slug}/...for sales invoices, purchase invoices, and products
GET /v1/business/{business_slug}/ reads one business: Business - Retrieve.
Creating a business is Business - Create. Read that schema before you POST. A created business still has its own slug. Do not assume the slug is the name you sent.
Identifiers
Business identifiers are a separate list: /v1/business/{business_slug}/identifiers/. They are not a replacement for slug. VAT codes and rates are constants on the business:
Read those operations when you need a code or a rate. Do not copy a rate into the client.