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A join link is a reusable, per-storefront signup URL you hand to an advertiser. An advertiser who signs up through it is provisioned as a sponsored buyer — a buyer account scoped to your storefront alone, sponsored by your organization. The buyer discovers and transacts only against your inventory; they never see the wider marketplace. Each link carries an approval policy that decides what happens the moment a buyer signs up: admit them immediately, hold them for your review, or refuse new signups. Once a buyer joins, you manage them through Sponsored buyers. All authenticated examples use the storefront base URL: 
https://api.interchange.io/api/v2/storefront
Authenticate every request with Authorization: Bearer $SCOPE3_API_KEY. The storefront is resolved from your API key’s seller customer context — there is no customerId path parameter. The one exception is Get join context, which is public and unauthenticated so the signup page can theme itself before the buyer has an account.

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Key concepts

  • Slug. Every link has a URL-safe slug (lowercase letters, numbers, hyphens). Omit it on creation and it is derived from the storefront name. The buyer visits joinPath (/join/{slug}); your UI or agent prepends its own origin.
  • Approval policy. Set at mint time and fixed for the life of the link:
    • auto_approve — signups become active sponsored buyers immediately.
    • manual_approve (default) — signups land pending until you approve them.
    • invite_only — admits signups the same way as manual_approve (they land pending); reserved for future invite-gated entry.
    • closed — refuses new signups; get-join-context reports a closed link as invalid.
  • Caps and expiry. maxUses caps total successful signups (omit for unlimited); expiresAt is an ISO-8601 expiry (omit for a link that never expires). uses counts successful signups so far.
  • Posture. Sponsored buyers are prepay day-one; the posture field future-proofs for credit terms.
  • Disable, don’t delete. Disabling a link soft-revokes it (active: false, revokedAt set). Buyers who already joined keep their accounts — disabling only stops new signups.
A join link only controls entry. After a buyer joins, their ability to transact is governed by their sponsored-buyer status, which you control independently. See Sponsored buyers.

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Task reference

Create join link

Mint a link for one of your storefronts

List join links

Every active link your organization owns

Disable join link

Soft-revoke a link to stop new signups

Get join context

Public brand-safe lookup for the signup page

Sponsored buyers

Manage the buyers who joined

All join-link tasks

Every operation in one place

Storefront onboarding

End-to-end seller setup

Errors

Shared error contract