diff --git a/tests/test_query_cross_dataset.py b/tests/test_query_cross_dataset.py
index c9c7d20..6f4c410 100644
--- a/tests/test_query_cross_dataset.py
+++ b/tests/test_query_cross_dataset.py
@@ -238,3 +238,32 @@ def test_without_dry_run_still_raises(self, monkeypatch: MonkeyPatch) -> None:
         _mock_all(monkeypatch)
         with pytest.raises(ValueError, match="non consentita"):
             layer_query(datasets=["ds_a"], mode="sql", sql="SELECT * FROM unknown_table")
+
+
+class TestMCPWrapperDryRun:
+    """Regressione: il wrapper MCP aggregate_ops.layer_query propaga dry_run.
+
+    La PR #457 ha aggiunto dry_run al backend (domain.layer) e al tool MCP
+    (server.py) ma non al wrapper intermedio (aggregate_ops.layer_query) →
+    TypeError: layer_query() got an unexpected keyword argument 'dry_run'
+    sul percorso reale del tool.
+    """
+
+    def test_wrapper_propagates_dry_run(self, monkeypatch: MonkeyPatch) -> None:
+        """Il wrapper MCP accetta dry_run e lo passa al backend."""
+        from toolkit.mcp.aggregate_ops import layer_query as mcp_layer_query
+
+        received: dict[str, object] = {}
+
+        def fake_backend(**kwargs: object) -> dict[str, object]:
+            received.update(kwargs)
+            return {"valid": True, "plan": "PLAN", "dry_run": True}
+
+        monkeypatch.setattr("toolkit.mcp.aggregate_ops._layer_query_core", fake_backend)
+
+        res = mcp_layer_query(
+            datasets=["ds_a"], layer="clean", mode="sql", sql="SELECT 1", dry_run=True
+        )
+
+        assert res["valid"] is True
+        assert received.get("dry_run") is True
diff --git a/toolkit/mcp/aggregate_ops.py b/toolkit/mcp/aggregate_ops.py
index 03809d6..a860470 100644
--- a/toolkit/mcp/aggregate_ops.py
+++ b/toolkit/mcp/aggregate_ops.py
@@ -52,6 +52,7 @@ def layer_query(
     sql: str | None = None,
     mart_index: int = 0,
     table: str | None = None,
+    dry_run: bool = False,
 ) -> dict[str, Any]:
     """Query unificata su layer RAW/CLEAN/MART.
 
@@ -71,6 +72,7 @@ def layer_query(
         sql: Query SQL per mode=sql.
         mart_index: Indice tabella mart (solo pipeline mode).
         table: Nome tabella mart (es ``"mart_top_sa"``).
+        dry_run: Se True (mode=sql), valida lo scope SQL e fa EXPLAIN senza eseguire.
 
     Raises:
         ToolkitClientError: se parametri invalidi o file non trovato.
@@ -97,6 +99,7 @@ def layer_query(
             sql=sql,
             mart_index=mart_index,
             table=table,
+            dry_run=dry_run,
         )
     except ValueError as exc:
         raise ToolkitClientError(str(exc), code=ErrorCode.INVALID_PARAMS) from exc