Both give a referral partner their own tracked lead source, so deals from them are attributed automatically. They differ only in how the partner sends you business. A sign up link gives the partner a unique link they fill out or pass along, which suits most accountants, realtors and referral partners. A Referral API is for a partner who wants to push client data to you from their own system or website form. Set up one lead source per partner under Lead sources and you can see exactly which businesses and deals each one brought in, from creation through to commission, without tracking it in a spreadsheet.
Connect a website form or system
A Portal administrator creates a scoped key in Settings → Connections → API. Use the REST getting-started guide and the current client-intake guide to send records to the correct lead source. Verify the key at the API root and use its returned source-channel slug. A lead-submission permission is write-only; it does not grant permission to read or update existing Businesses.
Keep the key server-side. When completing an application, use that record’s current contract_url for questions and file-transfer steps. Creating a business, completing intake and submitting an application are separate actions. If you only need a visitor to open your hosted intake, use the signup link instead of building an API integration.
Lead sources used to be called source channels. Brokers who send you deals are set up the same way, as a partner lead source.