Add Exmaples for how to use A2UI on Gemini Enterprise

samples/agent/adk/gemini_enterprise/README.md

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+# A2UI on Gemini Enterprise
+
+This folder contains examples and scripts to develop and use A2UI agents on **Gemini Enterprise**.
+
+## Folder Structure
+
+This directory is organized into two sub-folders depending the deployment methods:
+
+ - `cloud_run`: Contains scripts and configuration to deploy an agent to **Cloud Run**. This is suitable for building and deploying AI agents quickly, leveraging its speed and simplicity.
+   - Starts with `cloud_run/README.md`.
+
+ - `agent_engine`: Contains code to deploy to **Vertex AI Agent Engine**. Agent Engine provides additional features like agent context management, agent evaluation, agent lifecycle management, model-based conversation quality monitoring, and model tuning with context data.
+   - Starts with `agent_engine/README.md`.
+
+## Shared Resources
+
+- `a2ui_schema.py`: Contains the JSON schema for A2UI messages, used for validation during development and at runtime.
+- `a2ui_examples.py`: Provides several complete A2UI payload examples, such as Contact Cards and Action Confirmation modals.
+- `agent_executor.py`: A base implementation of an A2A (Agent-to-Agent) executor that handles A2UI validation and response formatting.
+
+## Registration in Gemini Enterprise
+
+Regardless of the deployment method, agents must be registered with Gemini Enterprise. This involves:
+1.  **Defining an A2A Agent Card**: Describing the agent's skills, name, and capabilities (including the **A2UI extension**).
+2.  **Configuring Authorization**: Setting up OAuth2 or other authentication mechanisms to allow the agent to talk to secure services. This is optional for Cloud Run deployment but **mandatory for Agent Engine deployment**.

samples/agent/adk/gemini_enterprise/agent_engine/.env.example

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+PROJECT_ID=<Your Google Cloud Project ID>
+LOCATION=<Your Google Cloud Location, for example: us-central1>
+STORAGE_BUCKET=<Your GCS Bucket starting with gs://>
+GEMINI_ENTERPRISE_APP_ID=<Your Gemini Enterprise App ID. You can create a new App or use an existing one.>
+AGENT_AUTHORIZATION=<Your Agent Authorization. See details in README.md>

samples/agent/adk/gemini_enterprise/agent_engine/README.md

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+# Register an A2UI Agent deployed on Vertex AI Agent Engine with Gemini Enterprise
+
+This sample demonstrates how to deploy an A2UI Agent on **Agent Engine** and
+register on **Gemini Enterprise**.
+
+## Overview
+
+High level steps:
+
+-   Config Authorization
+-   Setup environment variables
+-   Develop A2UI agent with ADK + A2A (sample code provided)
+-   Deploy the agent to Agent Engine
+-   Register the agent on Gemini Enterprise
+
+## Config Authorization
+
+Check **Before you begin** section and follow **Obtain authorization details**
+section on
+[Register and manage A2A agents](https://docs.cloud.google.com/gemini/enterprise/docs/register-and-manage-an-a2a-agent).
+Download JSON that looks like:
+
+```
+{
+    "web": {
+        "client_id": "<client id>",
+        "project_id": "<Google Cloud project id>",
+        "auth_uri": "https://accounts.google.com/o/oauth2/auth",
+        "token_uri": "https://oauth2.googleapis.com/token",
+        "auth_provider_x509_cert_url": "https://www.googleapis.com/oauth2/v1/certs",
+        "client_secret": "<secret>",
+        "redirect_uris": [
+            "https://vertexaisearch.cloud.google.com/oauth-redirect",
+            "https://vertexaisearch.cloud.google.com/static/oauth/oauth.html"
+        ]
+    }
+}
+```
+
+NOTE: For this deployment, you can skip the rest of **Register and manage A2A
+agents** page.
+
+Replace **YOUR_CLIENT_ID** with `client_id` which can be found in the downloaded
+json and save the following as **authorizationUri**
+
+```
+https://accounts.google.com/o/oauth2/v2/auth?client_id=<YOUR_CLIENT_ID>&redirect_uri=https%3A%2F%2Fvertexaisearch.cloud.google.com%2Fstatic%2Foauth%2Foauth.html&scope=https%3A%2F%2Fwww.googleapis.com%2Fauth%2Fcloud-platform&include_granted_scopes=true&response_type=code&access_type=offline&prompt=consent
+```
+
+In your console, run this:
+
+```
+curl -X POST \
+   -H "Authorization: Bearer $(gcloud auth print-access-token)" \
+   -H "Content-Type: application/json" \
+   -H "X-Goog-User-Project: <YOUR_PROJECT_ID>" \
+   "https://<ENDPOINT_LOCATION>-discoveryengine.googleapis.com/v1alpha/projects/<YOUR_PROJECT_ID>/locations/<LOCATION>/authorizations?authorizationId=<AUTH_ID>" \
+   -d '{
+      "name": "projects/<YOUR_PROJECT_ID>/locations/<LOCATION>/authorizations/<AUTH_ID>",
+      "serverSideOauth2": {
+         "clientId": "<OAUTH_CLIENT_ID>",
+         "clientSecret": "<OAUTH_CLIENT_SECRET>",
+         "authorizationUri": "<OAUTH_AUTH_URI>",
+         "tokenUri": "<OAUTH_TOKEN_URI>"
+      }
+   }'
+'
+```
+
+Replace the following:
+
+-   **YOUR_PROJECT_ID**: the ID of your project. There are 3 occasions
+-   **ENDPOINT_LOCATION**: the multi-region for your API request. Specify one of
+    the following values:
+    -   *us* for the US multi-region
+    -   *eu* for the EU multi-region
+    -   *global* for the Global location
+-   **LOCATION**: the multi-region of your data store: *global*, *us*, or *eu*.
+    There are 2 occasions
+-   **AUTH_ID**: The ID of the authorization resource. This is an arbitrary
+    alphanumeric ID that you define. You need to reference this ID later when
+    registering an Agent that requires OAuth support. There are 2 occasions.
+-   **OAUTH_CLIENT_ID**: copy `client_id` from the downloaded JSON.
+-   **OAUTH_CLIENT_SECRET**: copy `client_secret` from the downloaded JSON.
+-   **OAUTH_AUTH_URI**: the value of **authorizationUri**. See above.
+-   **OAUTH_TOKEN_URI**: copy `token_uri` from the downloaded JSON.
+
+NOTE: if `$(gcloud auth print-access-token)` does not work for you, replace it
+with `$(gcloud auth application-default print-access-token)` and try again.
+
+As result, you will get **AGENT_AUTHORIZATION** like this:
+
+```
+projects/PROJECT_NUMBER/locations/global/authorizations/<AUTH_ID>
+```
+
+The value will be used as an environment variable described below.
+
+NOTE: if you already have an agent that is deployed to Agent Engine, skip to
+**Manually Register An Agent** section.
+
+## Setup Environment Variables
+
+1.  **Copy `.env.example`:** Duplicate the `.env.example` file and rename it to
+    `.env`.
+    -   `cd /path/to/a2ui_on_agentengine`
+    -   `cp .env.example .env`
+2.  **Fill `.env`:** Update the `.env` file with your specific Google Cloud
+    project details:
+    *   `PROJECT_ID`: Your Google Cloud Project ID.
+    *   `LOCATION`: The Google Cloud region you want to deploy the agent in (e.g.,
+        `us-central1`). This location is **not** the same as the *location* used
+        in the command above.
+    *   `STORAGE_BUCKET`: A Google Cloud Storage bucket name for staging. It
+        starts with **"gs://"**.
+    *   `GEMINI_ENTERPRISE_APP_ID`: Your Gemini Enterprise Application ID. You
+        can create a new App or use an existing one on Google Cloud Gemini Enterprise.
+    *   `AGENT_AUTHORIZATION`: the value **AGENT_AUTHORIZATION** obtained above.
+
+## Running the Script
+
+The `main.py` script performs the following actions:
+
+1.  Initializes the Vertex AI client.
+2.  Defines a sample "Contact Card Agent" skill and creates an agent card.
+3.  Creates a local `A2aAgent` instance.
+4.  Deploys the agent to Vertex AI Agent Engine (`client.agent_engines.create`).
+5.  Fetches the deployed agent's card.
+6.  Registers the agent on Gemini Enterprise using the Discovery Engine API.
+
+To run the script using `uv`:
+
+1.  **Navigate to the script directory:**
+    -   `cd /path/to/a2ui_on_agentengine`
+2.  **Create and activate a virtual environment:**
+    -   `uv venv source`
+    -   `.venv/bin/activate`
+3.  **Install dependencies:**
+    -   `uv sync`
+4.  **Run the script:**
+    -   `uv run main.py`
+    -   It may take 5-10 minutes to finish.
+
+## Customization
+
+To build your own agent, you will need to:
+
+*   Implement your agent's logic, by modifying or replacing `agent_executor.py`
+    and the `AdkAgentToA2AExecutor` class.
+*   Adjust the `agent_name`, `display_name`, and `description` when calling
+    `_register_agent_on_gemini_enterprise` in `main.py`.
+
+## Manually Register An Agent
+
+If you have an Agent that is already deployed to Agent Engine, you can manually
+register it on Gemini Enterprise without running "main.py" script.
+
+1.  Complete **Config Authorization** section above.
+2.  Open Google Cloud **Gemini Enterprise**.
+3.  Click on the **App** you want to register your agent.
+    -   If you don't see the app being listed, click **Edit** to switch location
+4.  Select **Agents** from the left nav bar.
+5.  Click **Add agent** and select **Add** on **A2A** card.
+6.  Copy this following JSON to the "Agent Card JSON" input box.
+
+    ```
+    {
+      "name": "Test Contact Card Agent",
+      "url": "https://<LOCATION>-aiplatform.googleapis.com/v1beta1/<RESOURCE_NAME>/a2a",
+      "description": "A helpful assistant agent that can find contact card s.",
+      "skills": [
+        {
+          "description": "A helpful assistant agent that can find contact cards.",
+          "tags": [
+            "Contact-Card"
+          ],
+          "name": "Contact Card Agent",
+          "examples": [
+            "Who is John Doe?",
+            "List all contact cards."
+          ],
+          "id": "contact_card_agent"
+        }
+      ],
+      "version": "1.0.0",
+      "capabilities": {
+        "streaming": false,
+        "extensions": [
+          {
+            "uri": "https://a2ui.org/a2a-extension/a2ui/v0.8",
+            "description": "Ability to render A2UI",
+            "required": false,
+            "params": {
+              "supportedCatalogIds": [
+                "https://a2ui.org/specification/v0_8/standard_catalog_definition.json"
+              ]
+            }
+          }
+        ]
+      },
+      "protocolVersion": "0.3.0",
+      "defaultOutputModes": [
+        "application/json"
+      ],
+      "defaultInputModes": [
+        "text/plain"
+      ],
+      "supportsAuthenticatedExtendedCard": true,
+      "preferredTransport": "HTTP+JSON"
+    }
+    ```
+
+    Replace **LOCATION** and **RESOURCE_NAME**.
+
+    -   LOCATION is where you deploy your agent. For example; us-central1.
+    -   RESOURCE_NAME can be found on Google Cloud **Agent Engine**: click the agent;
+        click **Service Configuration**; select **Deployment details**; copy
+        **Resource name**.
+
+    Update *name*, *description*, *skills*, *version* as needed. Leave other
+    values unchanged.
+
+7.  Click **Preview Agent Details**
+
+8.  Click **Next**
+
+9.  Fill the **Agent authorization** form:
+
+    -   Copy `client_id`, `client_secret`, `token_uri` from the downloaded JSON.
+    -   Copy **authorizationUri** value from the above to **Authorization URL**.
+    -   Leave **Scopes** field empty.
+    -   Click **Finish**
+
+## Test Your Agent
+
+1.  Open Google Cloud Console and search for **"Gemini Enterprise"** and click on it.
+2.  Open the project you used in the above setting.
+3.  Click on the **App** you used to register your agent.
+    -   If you don't see your app being listed, click **"Edit"** to switch
+        location
+4.  Select **"Agents"** from the left nav bar.
+5.  Click the three-dot button on the **"Actions"** column and select
+    **"Previwe"** menu.
+6.  It will open Gemini Enterprise Agent page.
+7.  Try queries like *"Find contact card of Sarah"*.
+    -   If this is the first time you start a chat with the agent, it will ask
+        for manual authorization.
+8.  You should see a Contact Card being rendered on Gemini Enterprise.

samples/agent/adk/gemini_enterprise/agent_engine/__init__.py

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+# This file makes this directory a Python package