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A partner can offer one sales agent to many publishers. To sell through that agent, a publisher connects their Seller Account to it. V3 does this through one form, the partner connection form, so the partner’s own setup questions and your credentials never pass through a chat.

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Open the form

Call save_inventory_source with only the agent’s agentId.
The call creates nothing. It returns the form for that agent, and you complete the connection there. Only a Seller Account can open it, and only an account administrator signed in directly can read or complete it. A Buyer Account is refused with a wrong-account error. agentId stands alone. Sending it with any other save_inventory_source field, such as endpointUrl, authenticationType or name, is refused with VALIDATION_FAILED and names the extra field. The form owns those values for a partner’s agent, and a credential is never a model-visible input. An agentId the account cannot connect to is refused before the form opens. To change or add a source you operate yourself, keep using save_inventory_source without agentId.
The form opens as an MCP app, so it needs a host that renders them. See MCP Apps host.

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What the form asks for

The partner publishes how a publisher connects. The form shows what the partner published and nothing else:
  • Connection type. Shown only when the partner publishes more than one.
  • Endpoint. An address field appears only when the partner’s setup asks the publisher for one, for example a tenant URL. When the partner serves every publisher from one address, the form asks for none. Apostra validates the address you enter.
  • Partner fields. Any further fields the partner’s setup defines, such as a source name.
  • How to authenticate. Shown only when the partner offers more than one method. Credentials are entered in password fields. They are used to connect and are not shown again.
Apostra decides what is required and what is refused. When a value is not accepted, the form shows the message Apostra returns and keeps what you typed so you can correct it.

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What happens when you connect

  1. Apostra creates your source attached to the partner’s shared agent.
  2. Apostra completes the connection. The connection is accepted and validation starts.
  3. The source goes live once validation passes and the agent is certified. The agent’s single certification covers every publisher connected to it.
If the source is created but completing the connection fails, the form keeps the source and offers only the step still to do. Connecting again does not create a second source. When your account is already connected to the agent, the form says so and asks for nothing.

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Partner invites

A publisher who accepts a partner’s invite connects through the same form. The existing invite page keeps serving accepted invites until it moves to the form.