Setting {{ unsubscribe }} link in htmlcontent of API call

We use the https://api.brevo.com/v3/smtp/email API endpoint to create transactional emails. We would like to add a link to the unsubscribe page of Brevo. How can we do this?
We tried to use the link href=« {{ unsubscribe }} » but this gives a ‹ Template Render Error ›.

Anyone any idea?