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Preview. v2 remains the stable, default API. Selecting v3 in the documentation picker does not change an integration. Every authenticated Buyer or Seller Account can connect to v3; the tools returned still depend on that account’s permissions and resource access.
The v3 Agent Surface is one MCP endpoint whose tools follow the account you authenticated as:
v3 is intentionally an agent-facing MCP contract, not a versioned REST replacement. Integrations that require REST should continue to use the stable v2 REST APIs; v2 is not deprecated. v3 and v2 call the same underlying Interchange services and work with the same account data. Instead of choosing a buyer or seller URL, connect once and call get_status. It tells you which account you are in, whether that account is ready to work, what is blocking it, and which other accounts you may switch to.

Connect to v3

Configure an MCP client, authenticate, verify the current account, and make the first calls.

Understand the model

Learn how accounts, nouns, verbs, Pages, and tool discovery fit together.

Build a buyer workflow

Create an advertiser and campaign, request proposals, stage media buys, and launch explicitly.

Build a seller workflow

Read readiness, configure identity and inventory, operate work, and inspect delivery.

Use shared workflows

Navigate accounts, search public documentation, and file or track asks.

Browse the tool catalog

See which tools belong to every account, buyers, sellers, or MCP Apps.

Review preview limits

Know what remains on v2 and which fields or transitions are not complete.

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What changes from v2

v3 uses shared read verbs where the shape is safe to generalize:
  • search lists or searches a supported kind.
  • get reads one object and optional related detail.
  • save_<noun> creates or updates one typed noun.
  • Domain actions such as request_proposals and get_delivery remain explicit.
  • open_page hands sensitive or interactive work to a human-facing Page.
There is no generic v3 dispatcher. The input schema returned by tools/list is the contract for the current account.

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Account kinds

In a buyer account, search({kind: "seller"}) lists exact Storefront targets with account selection, billing, connection, and advertiser activation state. Use search({kind: "connection"}) or get for existing grants, and save_connection for selection, billing, authorization, provider-account selection, advertiser mapping, or removal. Authorization returns a browser URL; provider credentials are never accepted in an MCP tool call. When an agent already has exact Storefront ids, it can fetch up to 50 in one bounded read instead of issuing one get call per seller:
Results preserve the requested order and report unavailable ids in objects.missingIds. get remains the singular exact-object read. For an account that has not yet been classified as a Buyer or Seller Account, get_status and switch_account remain available for orientation and account navigation without exposing an operational tool catalog.

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Current maturity

The Seller surface is the broadest. The Buyer surface supports seller connections, campaign authoring, proposal requests, media-buy staging, and explicit campaign launch. Some lifecycle transitions and advanced policy fields still require v2; the preview limitations page is the authoritative list. v3 is a facade over the same Interchange services and account data as v2. It is a different agent contract, not a second platform, and no v2 deprecation is proposed.