fix(mcp): suppress third-party deprecation warnings from client responses (#38401)

superset/mcp_service/app.py

@@ -314,6 +314,24 @@ from superset.core.mcp.core_mcp_injection import (  # noqa: E402
 
 initialize_core_mcp_dependencies()
 
+# Suppress known third-party deprecation warnings that leak to MCP clients.
+# The MCP SDK captures Python warnings and forwards them to clients via
+# server log entries, wasting LLM tokens and causing clients to act on
+# irrelevant internal warnings. These warnings come from transitive imports
+# triggered by tool/schema registration below.
+import warnings  # noqa: E402
+
+warnings.filterwarnings(
+    "ignore",
+    category=DeprecationWarning,
+    module=r"marshmallow\..*",
+)
+warnings.filterwarnings(
+    "ignore",
+    category=FutureWarning,
+    module=r"google\..*",
+)
+
 # Import all MCP tools to register them with the mcp instance
 # NOTE: Always add new tool imports here when creating new MCP tools.
 # Tools use the @tool decorator from `superset-core` and register automatically

superset/mcp_service/server.py

@@ -36,6 +36,32 @@ from superset.mcp_service.storage import _create_redis_store
 logger = logging.getLogger(__name__)
 
 
+def _suppress_third_party_warnings() -> None:
+    """Suppress known third-party deprecation warnings from MCP responses.
+
+    The MCP SDK captures Python warnings and forwards them to clients via
+    ``mcp.server.lowlevel.server:Warning:`` log entries.  This wastes LLM
+    tokens and causes clients to try to "fix" irrelevant internal warnings.
+
+    Suppressed warnings:
+    - marshmallow ``RemovedInMarshmallow4Warning`` (triggered during
+      database engine schema instantiation)
+    - google.api_core ``FutureWarning`` (Python version support notices)
+    """
+    import warnings
+
+    warnings.filterwarnings(
+        "ignore",
+        category=DeprecationWarning,
+        module=r"marshmallow\..*",
+    )
+    warnings.filterwarnings(
+        "ignore",
+        category=FutureWarning,
+        module=r"google\..*",
+    )
+
+
 def configure_logging(debug: bool = False) -> None:
     """Configure logging for the MCP service."""
     import sys
@@ -179,6 +205,7 @@ def run_server(
     """
 
     configure_logging(debug)
+    _suppress_third_party_warnings()
 
     # DO NOT IMPORT TOOLS HERE!! IMPORT THEM IN app.py!!!!!
 

tests/unit_tests/mcp_service/test_mcp_server.py

@@ -109,6 +109,40 @@ def test_create_event_store_uses_default_config_values():
             )
 
 
+def test_suppress_third_party_warnings():
+    """Third-party deprecation warnings filters are installed."""
+    import re
+    import warnings
+
+    from superset.mcp_service.server import _suppress_third_party_warnings
+
+    _suppress_third_party_warnings()
+
+    # Verify marshmallow DeprecationWarning filter is installed
+    marshmallow_filters = [
+        f
+        for f in warnings.filters
+        if f[0] == "ignore"
+        and f[2] is DeprecationWarning
+        and isinstance(f[3], re.Pattern)
+        and f[3].pattern == r"marshmallow\..*"
+    ]
+    assert len(marshmallow_filters) >= 1, (
+        "Expected marshmallow DeprecationWarning filter"
+    )
+
+    # Verify google FutureWarning filter is installed
+    google_filters = [
+        f
+        for f in warnings.filters
+        if f[0] == "ignore"
+        and f[2] is FutureWarning
+        and isinstance(f[3], re.Pattern)
+        and f[3].pattern == r"google\..*"
+    ]
+    assert len(google_filters) >= 1, "Expected google FutureWarning filter"
+
+
 def test_create_event_store_returns_none_when_redis_store_fails():
     """EventStore returns None when Redis store creation fails."""
     config = {