Gemini MCP Server

import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js"; import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js"; import { config } from 'dotenv'; import { z } from "zod"; import { GeminiApiClient } from './gemini_api_client'; import fetch from 'node-fetch'; // Immediately send the startup message before anything else can write to stdout process.stdout.write(JSON.stringify({ jsonrpc: "2.0", method: "startup", params: { transport: "stdio" } }) + '\n'); // Redirect stdout to stderr for everything else const originalStdoutWrite = process.stdout.write.bind(process.stdout); process.stdout.write = (chunk: any, ...args: any[]) => { return process.stderr.write(chunk, ...args); }; // Redirect console methods to stderr const consoleMethods = ['log', 'info', 'warn', 'error', 'debug'] as const; consoleMethods.forEach(method => { (console as any)[method] = (...args: any[]) => process.stderr.write(`[${method}] ` + args.join(' ') + '\n'); }); // Suppress npm and Node.js startup messages process.env.NODE_ENV = 'production'; process.env.NO_UPDATE_NOTIFIER = '1'; process.env.SUPPRESS_NO_CONFIG_WARNING = 'true'; process.env.npm_config_loglevel = 'silent'; // Load environment variables config(); const GEMINI_API_KEY = process.env.GEMINI_API_KEY ?? ''; if (!GEMINI_API_KEY) { console.error('GEMINI_API_KEY environment variable is required'); process.exit(1); } // Model ID for Gemini const MODEL_ID = 'gemini-2.0-flash'; // Define tool schemas const generateTextSchema = z.object({ prompt: z.string().min(1), temperature: z.number().min(0).max(1).optional(), maxOutputTokens: z.number().min(1).max(8192).optional(), topK: z.number().min(1).max(40).optional(), topP: z.number().min(0).max(1).optional(), stream: z.boolean().optional(), }); type GenerateTextParams = z.infer<typeof generateTextSchema>; class GeminiMCPServer { private apiClient: GeminiApiClient; private server: McpServer; private transport: StdioServerTransport; private chatHistory: Array<{ role: string, parts: Array<{ text: string }> }> = []; constructor() { this.apiClient = new GeminiApiClient(GEMINI_API_KEY, MODEL_ID); this.server = new McpServer({ name: "gemini", version: "1.0.0", capabilities: { tools: { generate_text: { description: "Generate text using Gemini Pro model", streaming: true } } } }); this.transport = new StdioServerTransport(); } private async generateText(params: GenerateTextParams) { try { const { prompt, temperature = 0.7, maxOutputTokens = 8192, topK, topP, stream = false } = params; console.log('Sending message to Gemini:', prompt); // Add user message to history this.chatHistory.push({ role: 'user', parts: [{ text: prompt }] }); // Make a direct API call to Gemini const url = `https://generativelanguage.googleapis.com/v1beta/models/${MODEL_ID}:generateContent?key=${GEMINI_API_KEY}`; const body = { contents: this.chatHistory, generationConfig: { temperature, maxOutputTokens, topK, topP, } }; const response = await fetch(url, { method: 'POST', headers: { 'Content-Type': 'application/json', }, body: JSON.stringify(body), }); if (!response.ok) { const errorText = await response.text(); throw new Error(`Gemini API error (${response.status}): ${errorText}`); } const responseData = await response.json(); if (!responseData.candidates || !responseData.candidates[0] || !responseData.candidates[0].content) { throw new Error('Invalid response from Gemini API'); } // Extract the text from the response const responseText = responseData.candidates[0].content.parts .map((part: any) => part.text || '') .join(''); console.log('Received response from Gemini:', responseText); // Add assistant response to history this.chatHistory.push(responseData.candidates[0].content); return { content: [{ type: "text" as const, text: responseText }] }; } catch (err) { console.error('Error generating content:', err); return { content: [{ type: "text" as const, text: err instanceof Error ? err.message : 'Internal error' }], isError: true }; } } async start() { try { console.info('Initializing Gemini MCP server...'); // Register generate_text tool this.server.tool( "generate_text", generateTextSchema.shape, async (args: GenerateTextParams) => this.generateText(args) ); // Restore stdout for MCP communication process.stdout.write = originalStdoutWrite; // Connect using stdio transport await this.server.connect(this.transport); console.info('Server started successfully and waiting for messages...'); } catch (error) { console.error('Failed to start server:', error); process.exit(1); } } async stop() { try { // Note: Disconnect is not yet supported in MCP SDK // await this.server.disconnect(); console.info('Server stopped successfully'); } catch (error) { console.error('Error stopping server:', error); process.exit(1); } } } // Handle shutdown gracefully process.on('SIGINT', () => { console.info('Server shutting down'); process.exit(0); }); // Handle uncaught errors process.on('uncaughtException', (error) => { console.error('Uncaught exception:', error); process.exit(1); }); process.on('unhandledRejection', (reason) => { console.error('Unhandled rejection:', reason); process.exit(1); }); // Start the server const server = new GeminiMCPServer(); server.start().catch(error => { console.error('Unhandled error:', error); process.exit(1); });