diff --git a/superset/mcp_service/chart/tool/get_chart_type_schema.py b/superset/mcp_service/chart/tool/get_chart_type_schema.py
index dc21f3c6203..896d54d3099 100644
--- a/superset/mcp_service/chart/tool/get_chart_type_schema.py
+++ b/superset/mcp_service/chart/tool/get_chart_type_schema.py
@@ -126,14 +126,27 @@ def _get_chart_type_schema_impl(
     """Pure logic for chart type schema lookup — no auth, no decorators."""
     adapter = _CHART_TYPE_ADAPTERS.get(chart_type)
     if adapter is None:
+        # Return a structured error matching ChartGenerationError's shape so
+        # MCP clients consuming the response see a populated error_type,
+        # message, details, and suggestions rather than a bare dict.
+        valid_types_str = ", ".join(VALID_CHART_TYPES)
         return {
-            "error": f"Unknown chart_type: {chart_type!r}",
+            "error": {
+                "error_type": "invalid_chart_type",
+                "message": f"Unknown chart_type: {chart_type!r}",
+                "details": (
+                    f"Chart type {chart_type!r} is not supported. "
+                    f"Must be one of: {valid_types_str}."
+                ),
+                "suggestions": [
+                    f"Use one of: {valid_types_str}",
+                    "Check spelling and ensure lowercase",
+                    "Call this tool again with a valid chart_type to see "
+                    "its schema and examples",
+                ],
+                "error_code": "INVALID_CHART_TYPE",
+            },
             "valid_chart_types": VALID_CHART_TYPES,
-            "hint": (
-                "Use one of the valid chart_type values listed above. "
-                "Call this tool again with a valid chart_type to see "
-                "its schema and examples."
-            ),
         }
 
     schema = adapter.json_schema()
diff --git a/tests/unit_tests/mcp_service/chart/tool/test_get_chart_type_schema.py b/tests/unit_tests/mcp_service/chart/tool/test_get_chart_type_schema.py
index f7f2d166a5a..1da1b587b01 100644
--- a/tests/unit_tests/mcp_service/chart/tool/test_get_chart_type_schema.py
+++ b/tests/unit_tests/mcp_service/chart/tool/test_get_chart_type_schema.py
@@ -70,6 +70,24 @@ class TestGetChartTypeSchema:
         assert "valid_chart_types" in result
         assert result["valid_chart_types"] == VALID_CHART_TYPES
 
+    def test_invalid_chart_type_returns_structured_error(self) -> None:
+        """Invalid chart_type must return a populated, structured error body.
+
+        Without this guarantee, MCP clients see an empty/unstructured payload
+        and cannot self-correct (Eval 26 Test 26.5).
+        """
+        result = _call_schema("nonexistent")
+        err = result["error"]
+        assert isinstance(err, dict)
+        assert err["error_type"] == "invalid_chart_type"
+        assert err["error_code"] == "INVALID_CHART_TYPE"
+        assert "nonexistent" in err["message"]
+        assert err["details"]
+        assert err["suggestions"]
+        # Suggestions must name at least one valid chart type so callers know
+        # what to try next.
+        assert any(vt in " ".join(err["suggestions"]) for vt in VALID_CHART_TYPES)
+
     def test_examples_match_chart_type(self) -> None:
         result = _call_schema("pie")
         for example in result["examples"]: