Choose how your storefront gets supply

Every storefront draws inventory from one or more inventory sources. The source path depends on what you already run and which system owns the sell-side lifecycle. This page is the canonical decision guide for setup.

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Open Inventory Sources

If your account is enrolled in the unified Inventory Sources preview, choose the context selector at the top of the Interchange seller navigation. The Storefront name means you are working at the overall Storefront level; a source name means you are managing that exact source. Choose All inventory sources to open the existing storefront-wide source list, or choose a named source to open its established detail page. The rest of the storefront navigation remains available in either context. Use Add inventory source at the bottom of the same selector to open the existing list with its provider choices expanded. You can start an ad-server connection, external sales agent, or modular source there without opening a second workspace. A shared source link restores the exact source ID. If that source is unavailable or you lack access, Interchange shows it as unavailable instead of opening a different source. Source-specific credentials, actions, and diagnostic state stay isolated to that source. Protocol diagnostics are only exposed for an external sales agent you operate, not for managed integrations or official adapters. On a new storefront, Seller Setup shows one Add your first inventory source area rather than repeating the same action in the readiness checklist. Choose who operates the connection: Scope3-managed, Certified partner, or Operator-managed (bring your own agent). Custom modular composition is available as an advanced path. After the first source is connected, this area becomes a compact source-and-status list with Add another source collapsed under it. The ownership label and status mean different things. The ownership pill stays with the source; the status light changes as the connection moves from setup to connected or develops an observed issue. Setup is neutral. Yellow and red are only used for problems observed after the storefront is live.

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Decision table

Start from what you operate today.

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The five setup paths

The authoritative definition of each family:

AGENT is an external AdCP-compatible sales agent the Merchandising Agent connects to; MANAGED_SALES_AGENT is an operator-owned ad server with Interchange-managed sales-agent plumbing; LINKED_STOREFRONT is wholesale inventory discovered automatically from the ambient pool of LISTED, transacting storefronts (resolved at runtime, never persisted as a source row); MODULAR_SOURCE is a private composed implementation assembled from modules such as avails, booking, trafficking, and reporting. A standard modular recipe such as CitrusAd is presented as an ad-server connection, while custom compositions use the advanced modular-source workflow. Storefront-level ADAPTER dispatch is configured on the storefront, not as an inventory source.

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Ad-server connection

Pick this when you own an ad server — Google Ad Manager, FreeWheel, SpringServe, AdsWizz, or a provider with a standard recipe such as CitrusAd — and want to sell its inventory through your storefront. Buyers transact against your storefront while a supported direct integration or Interchange-managed sales agent reads the ad server’s existing ad units, placements, and products. The setup surface may hide that implementation difference because the seller outcome is the same. These sources use the ad-server connection and lifecycle endpoints (connect, save config, test, launch, deactivate, reactivate), not the generic external-agent create flow. Some providers use a managed ESA tenant; others, including CitrusAd, use a preconfigured private module recipe. That implementation detail does not change the seller or buyer experience. For what each ad server asks for and why, see Why Interchange needs access to your ad server. See also Get ad-server connection and Replace ad-server config.

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External sales agent (AGENT)

Pick this when you already run — or want to connect — your own AdCP-compatible sales agent reachable at a URL. You register it with the source endpoint, supplying the endpoint URL, protocol (MCP or A2A), and auth. Your Merchandising Agent then calls that agent for discovery and media buys. This is the only family created and updated through the generic inventory-source create and update flow. An external sales-agent source can declare two product paths:

• Agent-supplied: buyer briefs are sent to your sales agent and it answers live. Use this when the upstream agent already knows how to sell and rank its own products.
• Storefront-built: your source exposes raw products/components that Interchange caches, then the Merchandising Agent composes buyer-facing products from those cached components and your operating instructions.

For merchandising, cache success means Interchange can read stable component ids, pricing options, formats, publisher properties or other inventory selectors, delivery type, and execution metadata without making a live source call during buyer-request composition. If the source cannot provide a usable component cache, Murph reports that as a cache/readiness complaint; Agent-supplied brief discovery can still be healthy. Interchange only attempts wholesale product or signal catalog requests to an external sales agent when the Source supports the Storefront-built path and the Agent reports AdCP 3.1+ support. With the Agent-supplied path, buyer briefs and media buys call your sales agent live, and component-cache readiness is not used as a health signal. An Agent may support both product paths; its Source then selects one or both paths. See Create inventory source and Diagnose third-party sales agents.

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Linked storefront (LINKED_STOREFRONT)

Pick this when you want supply from other storefronts already transacting on the Interchange. Linked inventory is discovered automatically from the ambient pool of LISTED storefronts and resolved at runtime — there is no source row to create or manage. You participate by being LISTED; matching wholesale inventory surfaces to your storefront scoped by your own channel and geography.

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Modular (MODULAR_SOURCE)

Pick this when inventory and execution do not come from one compliant upstream agent. A modular source is composed from private modules — an avails feed, a booking ledger, trafficking, status sync, reporting import — and presents one buyer-facing surface. Use it when, for example, a publisher sends a periodic avails file, confirms bookings by hand, and uploads delivery reports after the campaign ends. See the Modular lifecycle guide.

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Storefront adapter (ADAPTER routing)

Pick this only when Scope3 supports an expert provider that should dispatch the whole buyer-facing storefront directly. The adapter is configured on the storefront itself; it is not an inventory source and cannot be added through an inventory-source form. This differs from an external AdCP sales agent, which is private upstream supply behind a storefront, and from a modular source, whose modules are combined behind the storefront. Adapter availability and lifecycle capabilities are provider-specific, so do not assume that an adapter automates booking, creative, or reporting unless its setup explicitly says so.

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Still unsure?

• You operate an ad server and want to sell its inventory → ad-server connection.
• You have an AdCP agent at a URL → external sales agent.
• You want inventory from the marketplace with nothing to connect → linked storefront.
• Your supply is stitched together from feeds and manual steps → modular.
• One supported provider should operate the whole storefront → storefront adapter.

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