Sends each person a 1:1 utility template message carrying the group invite link (Meta resolves the group id to the link at delivery). The template is auto-provisioned from Meta's Template Library on first use per channel. Joins arrive asynchronously on the group_participants_update webhook, so someone invited will not appear in participants until they accept.

Identify people by phones or by contactIds, but not both in the same request. Numbers must be in international format including the country code (+919958135900); bare local digits will not match a contact. Every number must already be a WhatsApp contact in this workspace. Nothing is sent unless all of them resolve, and the response names any that did not, so you can create those contacts with POST /contacts and invite again. Creating a contact raises new_contact_created, so any workflow listening for a new contact will run. The group must be active.

Each result carries the contactId it applies to, plus the phone it came from when the request used phones, so a failure can be traced back to the number you sent. The number is echoed normalised, without the leading +, so match on digits rather than on the exact string you sent.