@rnsk/mcp

Official stdio MCP server — run Runstack as a local subprocess in Cursor, Claude Desktop, and other command-based MCP hosts.

Source: https://runstack.engineer/docs/rnsk-mcp

@rnsk/mcp is a stdio MCP server. Your client spawns it as a subprocess; it forwards JSON-RPC to the hosted Runstack MCP API at https://app.runstack.engineer/mcp. Same registry and MCP tools as HTTP /mcp, without configuring a remote URL in the client.

Install (via npx)

Most hosts only need npx — no global install:

npx -y @rnsk/mcp

Set RUNSTACK_API_KEY in the environment. Get a key at API Keys (rnsk_…).

Cursor / Claude Desktop config

{
  "mcpServers": {
    "runstack": {
      "command": "npx",
      "args": ["-y", "@rnsk/mcp"],
      "env": {
        "RUNSTACK_API_KEY": "rnsk_..."
      }
    }
  }
}

Cursor: MCP settings (or .cursor/mcp.json in your project).
Claude Desktop: ~/Library/Application Support/Claude/claude_desktop_config.json on macOS (path varies on Windows/Linux).

Restart the client after saving.

Environment variables

Variable	Required	Description
`RUNSTACK_API_KEY`	Yes	Bearer token for `/mcp`
`RUNSTACK_MCP_URL`	No	Override MCP URL (default: `https://app.runstack.engineer/mcp`)

Never commit real keys; use env vars or your host’s secret UI.

stdio vs HTTP

	`@rnsk/mcp` (stdio)	HTTP `/mcp`
Transport	stdin/stdout	HTTPS JSON-RPC
Client setup	`command` + `args`	URL + `Authorization: Bearer`
Best for	IDE MCP, local subprocess hosts	Shared remote access, SDKs

To build a custom stdio server (not the Runstack bridge), see stdio MCP Server.