mcp-use/dist/src/connectors/stdio.js

A utility library for integrating Model Context Protocol (MCP) with LangChain, Zod, and related tools. Provides helpers for schema conversion, event streaming, and SDK usage.

import process from 'node:process';
import { Client } from '@modelcontextprotocol/sdk/client/index.js';
import { logger } from '../logging.js';
import { StdioConnectionManager } from '../task_managers/stdio.js';
import { BaseConnector } from './base.js';
export class StdioConnector extends BaseConnector {
    command;
    args;
    env;
    errlog;
    clientInfo;
    constructor({ command = 'npx', args = [], env, errlog = process.stderr, ...rest } = {}) {
        super(rest);
        this.command = command;
        this.args = args;
        this.env = env;
        this.errlog = errlog;
        this.clientInfo = rest.clientInfo ?? { name: 'stdio-connector', version: '1.0.0' };
    }
    /** Establish connection to the MCP implementation. */
    async connect() {
        if (this.connected) {
            logger.debug('Already connected to MCP implementation');
            return;
        }
        logger.debug(`Connecting to MCP implementation via stdio: ${this.command}`);
        try {
            // 1. Build server parameters for the transport
            // Merge env with process.env, filtering out undefined values
            let mergedEnv;
            if (this.env) {
                mergedEnv = {};
                // First add process.env values (excluding undefined)
                for (const [key, value] of Object.entries(process.env)) {
                    if (value !== undefined) {
                        mergedEnv[key] = value;
                    }
                }
                // Then override with provided env
                Object.assign(mergedEnv, this.env);
            }
            const serverParams = {
                command: this.command,
                args: this.args,
                env: mergedEnv,
            };
            // 2. Start the connection manager -> returns a live transport
            this.connectionManager = new StdioConnectionManager(serverParams, this.errlog);
            const transport = await this.connectionManager.start();
            // 3. Create & connect the MCP client
            this.client = new Client(this.clientInfo, this.opts.clientOptions);
            await this.client.connect(transport);
            this.connected = true;
            logger.debug(`Successfully connected to MCP implementation: ${this.command}`);
        }
        catch (err) {
            logger.error(`Failed to connect to MCP implementation: ${err}`);
            await this.cleanupResources();
            throw err;
        }
    }
    get publicIdentifier() {
        return {
            'type': 'stdio',
            'command&args': `${this.command} ${this.args.join(' ')}`,
        };
    }
}