chore: import upstream snapshot with attribution

python/samples/demos/mcp_server/agent_as_server.py

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+# /// script # noqa: CPY001
+# dependencies = [
+#   "semantic-kernel[mcp]",
+# ]
+# ///
+# Copyright (c) Microsoft. All rights reserved.
+import argparse
+import ipaddress
+import logging
+from typing import Annotated, Any, Literal
+
+import anyio
+from azure.identity.aio import AzureCliCredential
+
+from semantic_kernel.agents import AzureAIAgent, AzureAIAgentSettings
+from semantic_kernel.functions import kernel_function
+
+logger = logging.getLogger(__name__)
+
+"""
+This sample demonstrates how to expose an Agent as a MCP server.
+
+To run this sample, set up your MCP host (like Claude Desktop or VSCode Github Copilot Agents)
+with the following configuration:
+```json
+{
+    "mcpServers": {
+        "sk": {
+            "command": "uv",
+            "args": [
+                "--directory=<path to sk project>/semantic-kernel/python/samples/demos/mcp_server",
+                "run",
+                "agent_mcp_server.py"
+            ],
+            "env": {
+                "AZURE_AI_AGENT_PROJECT_CONNECTION_STRING": "<your azure connection string>",
+                "AZURE_AI_AGENT_MODEL_DEPLOYMENT_NAME": "<your azure model deployment name>",
+            }
+        }
+    }
+}
+```
+Alternatively, you can run this as a SSE server, by setting the same environment variables as above, 
+and running the following command:
+```bash
+uv --directory=<path to sk project>/semantic-kernel/python/samples/demos/mcp_server \
+run agent_mcp_server.py --transport sse --port 8000
+```
+This will start a server that listens for incoming requests on port 8000.
+
+In both cases, uv will make sure to install semantic-kernel with the mcp extra for you in a temporary venv.
+"""
+
+
+def is_loopback_host(host: str) -> bool:
+    """Return True if the host refers to a loopback interface (incl. IPv6 ::1)."""
+    if host == "localhost":
+        return True
+    try:
+        return ipaddress.ip_address(host).is_loopback
+    except ValueError:
+        return False
+
+
+def parse_arguments():
+    parser = argparse.ArgumentParser(description="Run the Semantic Kernel MCP server.")
+    parser.add_argument(
+        "--transport",
+        type=str,
+        choices=["sse", "stdio"],
+        default="stdio",
+        help="Transport method to use (default: stdio).",
+    )
+    parser.add_argument(
+        "--port",
+        type=int,
+        default=None,
+        help="Port to use for SSE transport (required if transport is 'sse').",
+    )
+    parser.add_argument(
+        "--host",
+        type=str,
+        default="127.0.0.1",
+        help=(
+            "Host/interface to bind the SSE server to (default: 127.0.0.1). "
+            "Binding to anything other than loopback (e.g. 0.0.0.0) exposes the server "
+            "to the network and should only be done on a trusted network with authentication added."
+        ),
+    )
+    args = parser.parse_args()
+    if args.transport == "sse" and args.port is None:
+        parser.error("--port is required when --transport is 'sse'.")
+    return args
+
+
+# Define a simple plugin for the sample
+class MenuPlugin:
+    """A sample Menu Plugin used for the sample."""
+
+    @kernel_function(description="Provides a list of specials from the menu.")
+    def get_specials(self) -> Annotated[str, "Returns the specials from the menu."]:
+        return """
+        Special Soup: Clam Chowder
+        Special Salad: Cobb Salad
+        Special Drink: Chai Tea
+        """
+
+    @kernel_function(description="Provides the price of the requested menu item.")
+    def get_item_price(
+        self, menu_item: Annotated[str, "The name of the menu item."]
+    ) -> Annotated[str, "Returns the price of the menu item."]:
+        return "$9.99"
+
+
+async def run(transport: Literal["sse", "stdio"] = "stdio", port: int | None = None, host: str = "127.0.0.1") -> None:
+    async with (
+        # 1. Login to Azure and create a Azure AI Project Client
+        AzureCliCredential() as creds,
+        AzureAIAgent.create_client(credential=creds) as client,
+    ):
+        agent = AzureAIAgent(
+            client=client,
+            definition=await client.agents.create_agent(
+                model=AzureAIAgentSettings().model_deployment_name,
+                name="Host",
+                instructions="Answer questions about the menu.",
+            ),
+            plugins=[MenuPlugin()],  # add the sample plugin to the agent
+        )
+        server = agent.as_mcp_server()
+
+        if transport == "sse" and port is not None:
+            import nest_asyncio
+            import uvicorn
+            from mcp.server.sse import SseServerTransport
+            from starlette.applications import Starlette
+            from starlette.middleware import Middleware
+            from starlette.middleware.trustedhost import TrustedHostMiddleware
+            from starlette.responses import PlainTextResponse
+            from starlette.routing import Mount, Route
+            from starlette.types import ASGIApp, Receive, Scope, Send
+
+            # A local MCP server is a security boundary, not a generic web server: it exposes
+            # tools, plugins and model providers backed by the developer's credentials. Without
+            # Host/Origin validation a malicious web page could use DNS rebinding to reach this
+            # loopback listener from the victim's browser and invoke the exposed MCP tools.
+            # The MCP spec therefore requires servers to validate Origin and bind to loopback.
+            allowed_hosts = [
+                "localhost",
+                "127.0.0.1",
+                "[::1]",
+                f"localhost:{port}",
+                f"127.0.0.1:{port}",
+                f"[::1]:{port}",
+            ]
+            allowed_origins = {
+                "http://localhost",
+                "http://127.0.0.1",
+                "http://[::1]",
+                f"http://localhost:{port}",
+                f"http://127.0.0.1:{port}",
+                f"http://[::1]:{port}",
+            }
+
+            class OriginValidationMiddleware:
+                """Reject requests with an untrusted Origin header (DNS-rebinding defense)."""
+
+                def __init__(self, app: ASGIApp) -> None:
+                    self.app = app
+
+                async def __call__(self, scope: Scope, receive: Receive, send: Send) -> None:
+                    if scope["type"] == "http":
+                        origin = dict(scope["headers"]).get(b"origin")
+                        if origin is not None:
+                            try:
+                                origin_value = origin.decode("ascii")
+                            except UnicodeDecodeError:
+                                origin_value = None
+                            if origin_value not in allowed_origins:
+                                response = PlainTextResponse("Forbidden: invalid Origin header", status_code=403)
+                                await response(scope, receive, send)
+                                return
+                    await self.app(scope, receive, send)
+
+            sse = SseServerTransport("/messages/")
+
+            async def handle_sse(request):
+                async with sse.connect_sse(request.scope, request.receive, request._send) as (
+                    read_stream,
+                    write_stream,
+                ):
+                    await server.run(read_stream, write_stream, server.create_initialization_options())
+
+            starlette_app = Starlette(
+                debug=False,
+                routes=[
+                    Route("/sse", endpoint=handle_sse),
+                    Mount("/messages/", app=sse.handle_post_message),
+                ],
+                middleware=[
+                    Middleware(TrustedHostMiddleware, allowed_hosts=allowed_hosts),
+                    Middleware(OriginValidationMiddleware),
+                ],
+            )
+
+            if not is_loopback_host(host):
+                logger.warning(
+                    "Binding the MCP SSE server to %s exposes it beyond loopback. The bundled Host/Origin "
+                    "checks only allow loopback callers; for a network-reachable or credentialed deployment "
+                    "add proper authentication (see the mcp_with_oauth sample) before doing this.",
+                    host,
+                )
+
+            nest_asyncio.apply()
+            uvicorn.run(starlette_app, host=host, port=port)  # nosec
+        elif transport == "stdio":
+            from mcp.server.stdio import stdio_server
+
+            async def handle_stdin(stdin: Any | None = None, stdout: Any | None = None) -> None:
+                async with stdio_server() as (read_stream, write_stream):
+                    await server.run(read_stream, write_stream, server.create_initialization_options())
+
+            await handle_stdin()
+
+
+if __name__ == "__main__":
+    args = parse_arguments()
+    anyio.run(run, args.transport, args.port, args.host)