If you are merging a group text, you can include details about all recipients in the "recipients" field. This field should have a "to" field with all the recipients, and optionally a "from" field, although that is currently unused.
The "recipients.to" field should be an array of recipients, with each entry containing the phone number of that recipient, and optionally their name.
The first recipient in this list which matches either the Person ID or one of their relationships will be used for all %contact_*% merge fields. The %contact_rels_first_name% field will return the list of first names.
For example, the request body above is merged as follows:
- %contact_name% is replaced with "Bob Alvarez"
- %contact_rels_first_name% is replaced with "Bob, Alice and Carol"