feat(mcp): serve HTML landing page on browser GET to MCP endpoint (#1072)

Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

Author: aaronsteers

airbyte/mcp/http_main.py

@@ -37,6 +37,8 @@
 import os
 from urllib.parse import urlparse
 
+from fastmcp_extensions import register_landing_page
+
 from airbyte.mcp.server import (
     DEFAULT_HTTP_HOST,
     DEFAULT_HTTP_PORT,
@@ -47,6 +49,18 @@
 
 logger = logging.getLogger(__name__)
 
+# Human-facing landing page shown when a browser GETs the MCP endpoint.
+MCP_LANDING_TITLE = "Airbyte MCP Server"
+MCP_LANDING_DOCS_URL = "https://docs.airbyte.com/ai-agents/"
+
+
+def _get_server_url() -> str:
+    """Return the public base URL from `MCP_SERVER_URL`, defaulting to localhost."""
+    return os.getenv(
+        MCP_SERVER_URL_ENV,
+        f"http://localhost:{DEFAULT_HTTP_PORT}",
+    )
+
 
 def main() -> None:
     """Start the Airbyte MCP server with HTTP transport."""
@@ -55,12 +69,24 @@ def main() -> None:
     # When deployed behind a path-stripping LB (MCP_SERVER_URL has a path
     # component like /cloud-mcp), serve the MCP endpoint at root so the
     # public URL is just the base path. Otherwise keep the FastMCP default.
-    server_url = os.getenv(
-        MCP_SERVER_URL_ENV,
-        f"http://localhost:{DEFAULT_HTTP_PORT}",
-    )
+    server_url = _get_server_url()
     mcp_path = "/" if urlparse(server_url).path.strip("/") else "/mcp"
 
+    # The advertised endpoint must match where the MCP route is actually mounted:
+    # the bare server URL when mounted at root, otherwise the server URL + mcp_path.
+    endpoint_url = server_url if mcp_path == "/" else server_url.rstrip("/") + mcp_path
+
+    # Serve a browser-friendly landing page on GET at the MCP path. In stateless
+    # mode FastMCP only binds POST/DELETE there, so this GET route does not
+    # interfere with MCP traffic.
+    register_landing_page(
+        app,
+        path=mcp_path,
+        title=MCP_LANDING_TITLE,
+        endpoint_url=endpoint_url,
+        docs_url=MCP_LANDING_DOCS_URL,
+    )
+
     if getattr(app, "auth", None) is None:
         logger.warning(
             "HTTP transport starting without authentication: no interactive "