I asked cursor to try with curl and this is what happened.
Yes — curl works, and everything succeeded. The mock node 
Mock node (MCP curl test) was created at the top level, right after ♖ DashBoard. Check your Workflowy to confirm.
Root cause of the Cursor problem: the raw responses show your server returns only structuredContent in tool results, with no content array:
{“result”: {“structuredContent”: {“results”: [“…”]}}}
Cursor’s MCP client apparently drops results that lack the standard content text blocks — that’s why I saw “(omitted)” for every call. The fix on your server: also include content: [{type: "text", text: "..."}] in each tool response.