MCP Server Gemini

Instructions

Implementation Reference

• src/enhanced-stdio-server.ts:517-658 (handler)

  The core handler function for the 'generate_text' tool. Validates inputs, constructs the Gemini API request with support for system instructions, JSON mode, grounding, conversation history, and safety settings, calls the API, and returns the generated text with metadata.
  private async generateText(id: any, args: any): Promise<MCPResponse> { try { // Validate parameters const validatedArgs = Validator.validateToolParams(ToolSchemas.generateText, args); const model = validatedArgs.model || 'gemini-2.5-flash'; logger.api(`Generating text with model: ${model}`); const modelInfo = GEMINI_MODELS[model as keyof typeof GEMINI_MODELS]; if (!modelInfo) { throw new Error(`Unknown model: ${model}`); } // Build generation config const generationConfig: any = { temperature: validatedArgs.temperature || 0.7, maxOutputTokens: validatedArgs.maxTokens || 2048, topK: validatedArgs.topK || 40, topP: validatedArgs.topP || 0.95 }; // Add JSON mode if requested if (validatedArgs.jsonMode) { generationConfig.responseMimeType = 'application/json'; if (validatedArgs.jsonSchema) { try { generationConfig.responseSchema = Validator.validateJSON(validatedArgs.jsonSchema); } catch (error) { logger.error('Invalid JSON schema provided:', error); throw new ValidationError('Invalid JSON schema format'); } } } // Build the request const requestBody: any = { model, contents: [ { parts: [ { text: Validator.sanitizeString(validatedArgs.prompt) } ], role: 'user' } ], generationConfig }; // Add system instruction if provided if (validatedArgs.systemInstruction) { requestBody.systemInstruction = { parts: [ { text: Validator.sanitizeString(validatedArgs.systemInstruction) } ] }; } // Add safety settings if provided if (args.safetySettings) { try { requestBody.safetySettings = typeof args.safetySettings === 'string' ? JSON.parse(args.safetySettings) : args.safetySettings; } catch (error) { console.error('Invalid safety settings JSON provided:', error); } } // Add grounding if requested and supported if (args.grounding && modelInfo.features.includes('grounding')) { requestBody.tools = [ { googleSearch: {} } ]; } // Handle conversation context if (args.conversationId) { const history = this.conversations.get(args.conversationId) || []; if (history.length > 0) { requestBody.contents = [...history, ...requestBody.contents]; } } // Call the API using the new SDK format const result = await this.genAI.models.generateContent({ model, ...requestBody }); const text = result.text || ''; // Update conversation history if needed if (args.conversationId) { const history = this.conversations.get(args.conversationId) || []; history.push(...requestBody.contents); history.push({ parts: [ { text } ], role: 'model' }); this.conversations.set(args.conversationId, history); } return { jsonrpc: '2.0', id, result: { content: [ { type: 'text', text } ], metadata: { model, tokensUsed: result.usageMetadata?.totalTokenCount, candidatesCount: result.candidates?.length || 1, finishReason: result.candidates?.[0]?.finishReason } } }; } catch (error) { console.error('Error in generateText:', error); return { jsonrpc: '2.0', id, error: { code: -32603, message: error instanceof Error ? error.message : 'Internal error' } }; } }
• src/enhanced-stdio-server.ts:222-289 (registration)

  Tool registration in getAvailableTools() method, defining the name, description, and inputSchema for the 'generate_text' tool advertised to MCP clients.
  { name: 'generate_text', description: 'Generate text using Google Gemini with advanced features', inputSchema: { type: 'object', properties: { prompt: { type: 'string', description: 'The prompt to send to Gemini' }, model: { type: 'string', description: 'Specific Gemini model to use', enum: Object.keys(GEMINI_MODELS), default: 'gemini-2.5-flash' }, systemInstruction: { type: 'string', description: 'System instruction to guide model behavior' }, temperature: { type: 'number', description: 'Temperature for generation (0-2)', default: 0.7, minimum: 0, maximum: 2 }, maxTokens: { type: 'number', description: 'Maximum tokens to generate', default: 2048 }, topK: { type: 'number', description: 'Top-k sampling parameter', default: 40 }, topP: { type: 'number', description: 'Top-p (nucleus) sampling parameter', default: 0.95 }, jsonMode: { type: 'boolean', description: 'Enable JSON mode for structured output', default: false }, jsonSchema: { type: 'string', description: 'JSON schema as a string for structured output (when jsonMode is true)' }, grounding: { type: 'boolean', description: 'Enable Google Search grounding for up-to-date information', default: false }, safetySettings: { type: 'string', description: 'Safety settings as JSON string for content filtering' }, conversationId: { type: 'string', description: 'ID for maintaining conversation context' } }, required: ['prompt'] } },
• src/utils/validation.ts:66-79 (schema)

  Zod schema definition for 'generate_text' tool parameters used for runtime validation in the handler.
  generateText: z.object({ prompt: z.string().min(1, 'Prompt is required'), model: CommonSchemas.geminiModel.optional(), systemInstruction: z.string().optional(), temperature: CommonSchemas.temperature.optional(), maxTokens: CommonSchemas.maxTokens.optional(), topK: CommonSchemas.topK.optional(), topP: CommonSchemas.topP.optional(), jsonMode: z.boolean().optional(), jsonSchema: CommonSchemas.jsonSchema.optional(), grounding: z.boolean().optional(), safetySettings: CommonSchemas.safetySettings.optional(), conversationId: CommonSchemas.conversationId.optional() }),