Cursor with a self-hosted MCP gateway

Cursor reads .cursor/mcp.json per project and a global one in your home directory. Each file lists its own servers, so a change means editing every copy. With Junctio the file contains one entry.

The setup

Create an endpoint in the gateway with api_key auth and issue a key, then write:

{
  "mcpServers": {
    "junctio": {
      "url": "https://mcp.example.com/mcp/main",
      "headers": {
        "Authorization": "Bearer jn_..."
      }
    }
  }
}

Junctio speaks Streamable HTTP and falls back to SSE for clients that ask for it, so the same URL keeps working across Cursor versions.

Per-project namespaces

A namespace is the unit Cursor sees. Give the frontend repo a namespace with the design system server and Playwright, give the backend one with Postgres and the deployment tools, and issue one endpoint per namespace. The key can be bound to a single endpoint, so a leaked project key cannot reach the other namespace.

Rate limits and the request log

Cursor’s agent mode can fan out tool calls quickly. An endpoint can cap requests per minute, counted per key, and answers over the limit with a 429 and Retry-After. The request log in the gateway shows every call with the upstream it went to and how long it took.

Related

Endpoints for the protocol details, Explore to import the servers you already have from a pasted mcp.json.

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