• Format XML, encoding UTF-8, transport HTTPS, access POST
• The interface is passive; the response is synchronous XML
• Document numbers are integer (max 2147483647)
• The whole XML post size limit is 19 MB; attachments are unlimited in count but must all fit within it.

• Input creates a new document or updates an existing one (matched by external key / number).
• Update behaviour is component-specific. Some components require xd_update=1 to modify an existing document (order, invoice, purchaseorder, quotation, expense, contract, transaction, resource, stockorder, event, absence, purchase); if a match is found and xd_update is not 1, the post is rejected.
• How much is updated also depends on the component:
  • Item (item) – partial update (the sent fields).
  • Invoice (invoice) – header partially, rows are replaced (delete + insert).
  • Delivery (delivery) – only partial update and adding (not fully replaced).
  • Customer/supplier – partial master-data update (name, email, phone) via xd_customer_update / xd_supplier_update (response 30 Updated).
  • For other transaction documents, post the whole document on update.
• A confirmed document generally cannot be modified – response Type=14 (confirmed or has linked documents). Exception: xd_updateconfirmed=1 for order, invoice, purchaseorder, stockreceipt.
• Behaviour is controlled by transport parameters; some inputs also support default value setup.

An exception, not default functionality. If needed, a custom after-save processing step can be added to the interface (by agreement with Directo) – extra logic that runs after the document is saved. Unlike transport parameters, this is not a standard setting but a case-by-case extension.