The landscape of software is shifting from Software-as-a-Service to Agents-as-a-Service, enabling AI agents to interoperate through standardized protocols like A2A. Developers can now build and commercialize these autonomous agents via Google Cloud Marketplace, integrating them with the Gemini Enterprise app. The process involves designing an architecture that bridges marketplace billing, security, and the Gemini Enterprise Agent Platform.Partners must join the Google Cloud Partner Network and adhere to specific listing requirements, including defining clear agent use cases and complying with the A2A protocol. A crucial element is the A2A Agent Card, a JSON file detailing the agent's capabilities, authentication methods, and endpoints. Agents must support public access or OAuth 2.0 for authentication and authorization.Technical requirements include following the A2A protocol documentation, which also guides the implementation of interactive user interfaces using A2UI. The A2A Agent Card is essential for displaying agent metadata and enabling the Gemini Enterprise app to locate endpoints, discover entry points, and determine authentication methods. Dynamic Client Registration (DCR) is supported to automate the OAuth client registration process.Publishing an agent involves selecting "AI Agent as a Service" in the Producer Portal, uploading the Agent Card, defining availability and pricing, and configuring backend procurement. Google Cloud then validates the agent before it becomes available on the Marketplace. The transaction and registration lifecycle involves distinct phases managed by a Billing Administrator, a Discovery Engine Administrator, and the end-user.Procurement is an asynchronous backend process initiated by a customer's subscription or private offer, triggering a notification to the partner. The partner approves the entitlement, records the transaction, and activates the subscription. Following procurement, the Discovery Engine Administrator links the purchase to their Gemini Enterprise environment through a synchronized registration flow, including a DCR handshake.Once registered, the agent becomes discoverable to end-users within the Gemini Enterprise app, who can then request access after proper identity authorization. This comprehensive process ensures secure, compliant, and governed access to third-party agents within an enterprise environment.