How your lead fills the partner's request, and how you read their reply back.
In Request mapping you say which of the partner's request fields each of your lead fields fills. Click into a value and drop in a macro — {phone}, {email}, {country}, {first_name} — plus any sub-id or tracking key the source sent. Apply small transforms where the partner is picky: E.164 phone, uppercase geo, split name.
Reading the reply is just as important, and it's a dot-path — a trail of keys into their JSON, like data.id for the id inside a data object. Four of them matter: the accept flag, the lead id, the autologin URL and the error message. Get the lead id right and status sync can match this lead back to the partner forever after.
You don't have to figure the paths out by hand. Paste the partner's example reply into “Fill the paths from a sample” and the CRM detects each one and offers to fill it. Where it can't, it names what that field is usually called. See Build a partner integration for the full walkthrough.