FIX: raise error for invalid explicit frequency in data adapters

src/sktime_mcp/data/adapters/file_adapter.py

@@ -100,8 +100,10 @@ def load(self) -> pd.DataFrame:
         # Set frequency if specified
         freq = self.config.get("frequency")
         if freq:
-            with contextlib.suppress(Exception):
+            try:
                 df = df.asfreq(freq)
+            except Exception as e:
+                raise ValueError(f"Invalid frequency '{freq}': {e}") from e
 
         self._data = df
 

src/sktime_mcp/data/adapters/pandas_adapter.py

@@ -5,7 +5,6 @@
 time index detection and validation.
 """
 
-import contextlib
 from typing import Any
 
 import pandas as pd
@@ -72,8 +71,10 @@ def load(self) -> pd.DataFrame:
         # Infer or set frequency
         freq = self.config.get("frequency")
         if freq:
-            with contextlib.suppress(Exception):
+            try:
                 df = df.asfreq(freq)
+            except Exception as e:
+                raise ValueError(f"Invalid frequency '{freq}': {e}") from e
         elif isinstance(df.index, pd.DatetimeIndex) and df.index.freq is None:
             # Try to infer frequency
             inferred_freq = pd.infer_freq(df.index)

tests/test_data_frequency_validation.py

@@ -0,0 +1,67 @@
+"""Tests for explicit frequency validation in data adapters."""
+
+from pathlib import Path
+
+import pytest
+
+from sktime_mcp.data.adapters.file_adapter import FileAdapter
+from sktime_mcp.data.adapters.pandas_adapter import PandasAdapter
+
+
+def test_pandas_adapter_rejects_invalid_explicit_frequency():
+    """Invalid user-provided frequency should fail instead of being ignored."""
+    adapter = PandasAdapter(
+        {
+            "type": "pandas",
+            "data": {
+                "date": ["2020-01-01", "2020-01-02", "2020-01-03"],
+                "value": [1, 2, 3],
+            },
+            "time_column": "date",
+            "target_column": "value",
+            "frequency": "not_a_freq",
+        }
+    )
+
+    with pytest.raises(ValueError, match="Invalid frequency 'not_a_freq'"):
+        adapter.load()
+
+
+def test_file_adapter_rejects_invalid_explicit_frequency(tmp_path: Path):
+    """Invalid explicit frequency should fail for file-backed data too."""
+    path = tmp_path / "series.csv"
+    path.write_text("date,value\n2020-01-01,1\n2020-01-02,2\n2020-01-03,3\n")
+
+    adapter = FileAdapter(
+        {
+            "type": "file",
+            "path": str(path),
+            "time_column": "date",
+            "target_column": "value",
+            "frequency": "not_a_freq",
+        }
+    )
+
+    with pytest.raises(ValueError, match="Invalid frequency 'not_a_freq'"):
+        adapter.load()
+
+
+def test_pandas_adapter_applies_valid_explicit_frequency():
+    """Valid explicit frequency should still be applied normally."""
+    adapter = PandasAdapter(
+        {
+            "type": "pandas",
+            "data": {
+                "date": ["2020-01-01", "2020-01-03"],
+                "value": [1, 3],
+            },
+            "time_column": "date",
+            "target_column": "value",
+            "frequency": "D",
+        }
+    )
+
+    data = adapter.load()
+
+    assert len(data) == 3
+    assert data.index.freqstr == "D"