chore: add a remote A2A knowledge agent for Agent Builder Assistant

PiperOrigin-RevId: 814484204

contributing/samples/adk_agent_builder_assistant/remote_agents/adk_knowledge_agent/README.md

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+# Agent Knowledge Agent
+
+An intelligent assistant for performing Vertex AI Search to find ADK knowledge
+and documentation.
+
+## Deployment
+
+This agent is deployed to Google Could Run as an A2A agent, which is used by
+the parent ADK Agent Builder Assistant.
+
+Here are the steps to deploy the agent:
+
+1. Set environment variables
+
+```bash
+export GOOGLE_CLOUD_PROJECT=your-project-id
+export GOOGLE_CLOUD_LOCATION=us-central1 # Or your preferred location
+export GOOGLE_GENAI_USE_VERTEXAI=True
+```
+
+2. Run the deployment command
+
+```bash
+$ adk deploy cloud_run --project=your-project-id --region=us-central1 --service_name=adk-agent-builder-knowledge-service --with_ui --a2a ./adk_knowledge_agent
+```

contributing/samples/adk_agent_builder_assistant/remote_agents/adk_knowledge_agent/__init__.py

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+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from . import agent

contributing/samples/adk_agent_builder_assistant/remote_agents/adk_knowledge_agent/agent.json

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+{
+  "capabilities": {},
+  "defaultInputModes": ["text/plain"],
+  "defaultOutputModes": ["application/json"],
+  "description": "Agent for performing Vertex AI Search to find ADK knowledge and documentation",
+  "name": "adk_knowledge_agent",
+  "skills": [
+    {
+      "id": "adk_knowledge_search",
+      "name": "ADK Knowledge Search",
+      "description": "Searches for ADK examples and documentation using the Vertex AI Search tool",
+      "tags": ["search", "documentation", "knowledge base", "Vertex AI", "ADK"]
+    }
+  ],
+  "url": "https://adk-agent-builder-knowledge-service-654646711756.us-central1.run.app/a2a/adk_knowledge_agent",
+  "version": "1.0.0"
+}

contributing/samples/adk_agent_builder_assistant/remote_agents/adk_knowledge_agent/agent.py

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+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import json
+from typing import Optional
+
+from google.adk.agents import LlmAgent
+from google.adk.agents.callback_context import CallbackContext
+from google.adk.models import LlmResponse
+from google.adk.tools.vertex_ai_search_tool import VertexAiSearchTool
+from google.genai import types
+
+VERTEXAI_DATASTORE_ID = "projects/adk-agent-builder-assistant/locations/global/collections/default_collection/dataStores/adk-agent-builder-sample-datastore_1758230446136"
+
+
+def citation_retrieval_after_model_callback(
+    callback_context: CallbackContext,
+    llm_response: LlmResponse,
+) -> Optional[LlmResponse]:
+  """Callback function to retrieve citations after model response is generated."""
+  grounding_metadata = llm_response.grounding_metadata
+  if not grounding_metadata:
+    return None
+
+  content = llm_response.content
+  if not llm_response.content:
+    return None
+
+  parts = content.parts
+  if not parts:
+    return None
+
+  # Add citations to the response as JSON objects.
+  parts.append(types.Part(text="References:\n"))
+  for grounding_chunk in grounding_metadata.grounding_chunks:
+    retrieved_context = grounding_chunk.retrieved_context
+    if not retrieved_context:
+      continue
+
+    citation = {
+        "title": retrieved_context.title,
+        "uri": retrieved_context.uri,
+        "snippet": retrieved_context.text,
+    }
+    parts.append(types.Part(text=json.dumps(citation)))
+
+  return LlmResponse(content=types.Content(parts=parts))
+
+
+root_agent = LlmAgent(
+    name="adk_knowledge_agent",
+    description=(
+        "Agent for performing Vertex AI Search to find ADK knowledge and"
+        " documentation"
+    ),
+    instruction="""You are a specialized search agent for an ADK knowledge base.
+
+      You can use the VertexAiSearchTool to search for ADK examples and documentation in the document store.
+      """,
+    model="gemini-2.5-flash",
+    tools=[VertexAiSearchTool(data_store_id=VERTEXAI_DATASTORE_ID)],
+    after_model_callback=citation_retrieval_after_model_callback,
+)

contributing/samples/adk_agent_builder_assistant/remote_agents/adk_knowledge_agent/requirements.txt

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+google-adk[a2a]==1.15.1