test(garden): surface MCP server error bodies

test_garden_layer.py

@@ -96,6 +96,10 @@ def test_batch_insert(garden_layer):
 def call_mcp_tool(tool_name: str, payload: Dict[str, Any]) -> Any:
     # Some ontology/traversal calls can be a bit slow depending on Virtuoso load.
     response = requests.post(MCP_URL, json={"tool": tool_name, "input": payload}, timeout=20)
+    if response.status_code >= 400:
+        raise AssertionError(
+            f"{tool_name} failed with {response.status_code}: {response.text}"
+        )
     response.raise_for_status()
     body = response.json()
     assert body.get("status") == "ok", f"{tool_name} failed: {body.get('detail') or 'unknown reason'}"