MCP server never loads in Cursor

Summary

In v0.40.0, the marketplace listing for this plugin shows "MCPs: 1 (Vercel)", but the MCP server never registers in Cursor. Root cause appears to be that the Cursor-specific manifest (.cursor-plugin/plugin.json) only declares:

"skills": "skills",
"agents": "agents",
"commands": "commands"

with no MCP entry. When Cursor materializes the plugin cache (~/.cursor/plugins/cache/cursor-public/vercel/<sha>/), it prunes files not declared in that manifest — including .mcp.json. The cache is a git checkout, and git status inside it shows .mcp.json (and .cursor-plugin/plugin.json, tests/, generated/) as working-tree deletions:

 D .cursor-plugin/plugin.json
 D .mcp.json
 D generated/build-from-skills.manifest.json
 ...

git show HEAD:.mcp.json confirms the repo ships a valid server definition (https://mcp.vercel.com, type http).

Result

• Plugin page in Cursor advertises 1 MCP server (metadata built from the full repo).
• No vercel MCP server ever appears in agent sessions or tool lists (loader reads the pruned on-disk cache).
• Compare: the Linear plugin's cache keeps its mcp.json and its server registers fine.

Expected

The MCP server advertised on the plugin page actually works after install: .mcp.json survives the cache step, the server registers in Cursor, and you get the Vercel OAuth prompt on first use.

Environment

• vercel-plugin 0.40.0 (cache sha 3d9d9cd0fe5d1bdaedb891135a5c45f19190b83f)
• Cursor 3.12.10, macOS arm64 (darwin 25.5.0)

Start with .cursor-plugin/plugin.json and compare its declared entries with .mcp.json and the Linear plugin's manifest behavior. Reproduce or inspect the Cursor cache step, then verify that .mcp.json is retained and the Vercel MCP server registers with its OAuth prompt.