chore: import upstream snapshot with attribution

contributing/samples/mcp/mcp_in_agent_tool_remote/README.md

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+# AgentTool with MCP Demo (SSE Mode)
+
+This demo shows how `AgentTool` works with MCP (Model Context Protocol) toolsets using **SSE mode**.
+
+## SSE vs Stdio Mode
+
+This demo uses **SSE (Server-Sent Events) mode** where the MCP server runs as a separate HTTP server:
+
+- **Remote connection** - Connects to server via HTTP
+- **Separate process** - Server must be started manually
+- **Network communication** - Uses HTTP/SSE for messaging
+
+For the **stdio (subprocess) version**, see [mcp_in_agent_tool_stdio](../mcp_in_agent_tool_stdio/).
+
+## Setup
+
+**Start the MCP simple-tool server in SSE mode** (in a separate terminal):
+
+```bash
+# Run the server using uvx (no installation needed)
+# Port 3000 avoids conflict with adk web (which uses 8000)
+uvx --from 'git+https://github.com/modelcontextprotocol/python-sdk.git#subdirectory=examples/servers/simple-tool' \
+    mcp-simple-tool --transport sse --port 3000
+```
+
+The server should be accessible at `http://localhost:3000/sse`.
+
+## Running the Demo
+
+```bash
+adk web contributing/samples
+```
+
+Then select **mcp_in_agent_tool_remote** from the list and interact with the agent.
+
+## Try These Prompts
+
+This demo uses **Gemini 2.5 Flash** as the model. Try these prompts:
+
+1. **Check available tools:**
+
+   ```
+   What tools do you have access to?
+   ```
+
+1. **Fetch and summarize JSON Schema specification:**
+
+   ```
+   Use the mcp_helper to fetch https://json-schema.org/specification and summarize the key features of JSON Schema
+   ```
+
+## Architecture
+
+```
+main_agent (root_agent)
+  │
+  └── AgentTool wrapping:
+        │
+        └── mcp_helper (sub_agent)
+              │
+              └── McpToolset (SSE connection)
+                    │
+                    └── http://localhost:3000/sse
+                          │
+                          └── MCP simple-tool server
+                                │
+                                └── Website Fetcher Tool
+```
+
+## Related
+
+- **Issue:** [#1112 - Using agent as tool outside of adk web doesn't exit cleanly](https://github.com/google/adk-python/issues/1112)
+- **Related Issue:** [#929 - LiteLLM giving error with OpenAI models and Grafana's MCP server](https://github.com/google/adk-python/issues/929)
+- **Stdio Version:** [mcp_in_agent_tool_stdio](../mcp_in_agent_tool_stdio/) - Uses local subprocess connection

contributing/samples/mcp/mcp_in_agent_tool_remote/__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_in_agent_tool_remote/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.
+
+from google.adk.agents import Agent
+from google.adk.tools import AgentTool
+from google.adk.tools.mcp_tool import McpToolset
+from google.adk.tools.mcp_tool.mcp_session_manager import SseConnectionParams
+
+# Create MCP toolset
+# This uses the simple-tool MCP server via SSE
+# You need to start the MCP server separately (see README.md)
+mcp_toolset = McpToolset(
+    connection_params=SseConnectionParams(
+        url="http://localhost:3000/sse",
+        timeout=10.0,
+        sse_read_timeout=300.0,
+    )
+)
+
+# Create sub-agent with MCP tools
+# This agent has direct access to MCP tools
+sub_agent = Agent(
+    name="mcp_helper",
+    description=(
+        "A helpful assistant with access to MCP tools for fetching websites."
+    ),
+    instruction="""You are a helpful assistant with access to MCP tools.
+
+When the user asks for help:
+1. Explain what tools you have available (website fetching)
+2. Use the appropriate tool if needed
+3. Provide clear and helpful responses
+
+You have access to a website fetcher tool via MCP. Use it to fetch and return website content.""",
+    tools=[mcp_toolset],
+)
+
+# Wrap sub-agent as an AgentTool
+# This allows the main agent to delegate tasks to the sub-agent
+# The sub-agent has access to MCP tools for fetching websites
+mcp_agent_tool = AgentTool(agent=sub_agent)
+
+# Create main agent
+# This agent can delegate to the sub-agent via AgentTool
+root_agent = Agent(
+    name="main_agent",
+    description="Main agent that can delegate to a sub-agent with MCP tools.",
+    instruction="""You are a helpful assistant. You have access to a sub-agent (mcp_helper)
+that has MCP tools for fetching websites.
+
+When the user asks for help:
+- If they need to fetch a website, call the mcp_helper tool
+- Otherwise, respond directly
+
+Always be helpful and explain what you're doing.""",
+    tools=[mcp_agent_tool],
+)