MCP Server Framework

Node.js library for building small Model Context Protocol servers, with an HTTP and a stdio transport and a shared registry file.

packages/robos-mcp-lib

robos-mcp-lib is a library first. Other packages (system-mcp, task-manager-mcp, workspace-manager-mcp and several more under packages/) call it to define their tools and resources.

What the library provides 

const { createMCPServer, startStdioTransport, listRegisteredServers } = require('../robos-mcp-lib/index');

const server = createMCPServer({
  appId: 'demo',
  tools: [{ name: 'hello', description: 'Say hello', handler: async () => 'hi' }],
  port: 19200,            // optional; omit to skip HTTP
});
  • JSON-RPC 2.0 handling for initialize, ping, tools/list, tools/call, resources/list and resources/read, reporting protocol version 2024-11-05. Any other method returns error -32601.
  • Naming. A tool named hello in app demo becomes robos_demo_hello; names that already start with robos_ are kept. A resource URI such as info becomes robos://demo/info.
  • HTTP transport (startHttp(port) or the port option): POST /mcp for JSON-RPC and GET /health, with permissive CORS headers.
  • stdio transport (startStdioTransport(server)): one JSON request per line on stdin, one response per line on stdout.
  • Registry. When a server starts it writes itself to ~/.config/robos/mcp/servers.json (app id, name, version, port, endpoint, tool names, resource URIs). stop() removes the entry. The MCP Router reads this file.

A tool handler’s return value is sent back as one text block (strings as-is, other values as pretty-printed JSON). If the handler throws, the result has isError: true and the error message.

The inspector window

main.js creates a demo server with the tools calculate_metrics and query_workspace and the resource system-info, and shows them in RobOS MCP Server Inspector & Framework. The tool results are fixed sample values. Click Call calculate_metrics to see the request and response in the protocol trace; Clear Trace empties it. The demo server has no HTTP port. Run it with npm start in packages/robos-mcp-lib (there is no .desktop launcher). npm test runs node --test.

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