Thanks for the detailed logs and for confirming the symptom matches thread 160620. Yep, it’s the same bug.
Quick summary: Stitch returns a huge tools/list response, around 287 KB, because each tool includes a duplicated outputSchema with hundreds of font enum values in DesignTheme. Cursor has an internal payload size limit, and when it’s exceeded the whole tools list gets silently dropped. That’s why the server shows as connected in Settings, but you see 0 tools. Connecting via Marketplace can behave differently for Stitch due to a different transport or schema variant, which explains the difference.
There’s a working workaround in the same thread, the solution by @And: MCP Server Connected (Green Dot) and Tools Discovered in Logs, but "0 tools" in UI and Agent - #10 by And
It’s a Node stdio proxy that strips outputSchema from the tools/list response and shrinks the payload to about 41 KB. After that, the tools show up correctly in the UI and in the agent. The mcp.json config is included there too.
On our side this is a bug. Even if there’s an internal limit, Cursor should show an error or warning in MCP Output, not silently drop the tools list. I’ve reported it internally, no ETA for a fix yet.