chore: import upstream snapshot with attribution

contributing/samples/mcp/mcp_stdio_notion_agent/README.md

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+# Notion MCP Agent
+
+This is an agent that is using Notion MCP tool to call Notion API. And it demonstrates how to pass in the Notion API key.
+
+Follow below instruction to use it:
+
+- Follow the installation instruction in below page to get an API key for Notion API:
+  https://www.npmjs.com/package/@notionhq/notion-mcp-server
+
+- Set the environment variable `NOTION_API_KEY` to the API key you obtained in the previous step.
+
+```bash
+export NOTION_API_KEY=<your_notion_api_key>
+```
+
+- Run the agent in ADK Web UI
+
+- Send below queries:
+
+  - What can you do for me ?
+  - Search `XXXX` in my pages.

contributing/samples/mcp/mcp_stdio_notion_agent/__init__.py

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+# Copyright 2026 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/mcp/mcp_stdio_notion_agent/agent.py

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+# Copyright 2026 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
+import os
+
+from dotenv import load_dotenv
+from google.adk.agents.llm_agent import LlmAgent
+from google.adk.tools.mcp_tool.mcp_toolset import MCPToolset
+from google.adk.tools.mcp_tool.mcp_toolset import StdioServerParameters
+
+load_dotenv()
+
+NOTION_API_KEY = os.getenv("NOTION_API_KEY")
+NOTION_HEADERS = json.dumps({
+    "Authorization": f"Bearer {NOTION_API_KEY}",
+    "Notion-Version": "2022-06-28",
+})
+
+root_agent = LlmAgent(
+    name="notion_agent",
+    instruction=(
+        "You are my workspace assistant. "
+        "Use the provided tools to read, search, comment on, "
+        "or create Notion pages. Ask clarifying questions when unsure."
+    ),
+    tools=[
+        MCPToolset(
+            connection_params=StdioServerParameters(
+                command="npx",
+                args=["-y", "@notionhq/notion-mcp-server"],
+                env={"OPENAPI_MCP_HEADERS": NOTION_HEADERS},
+            )
+        )
+    ],
+)