microsoft--mcp-for-beginners/translations/en/04-PracticalImplementation/samples/javascript

Sample

This is a JavaScript example for an MCP Server

Here’s an example of tool registration where we register a tool that makes a mock call to an LLM:

this.mcpServer.tool(
    'completion',
    {
    model: z.string(),
    prompt: z.string(),
    options: z.object({
        temperature: z.number().optional(),
        max_tokens: z.number().optional(),
        stream: z.boolean().optional()
    }).optional()
    },
    async ({ model, prompt, options }) => {
    console.log(`Processing completion request for model: ${model}`);
    
    // Validate model
    if (!this.models.includes(model)) {
        throw new Error(`Model ${model} not supported`);
    }
    
    // Emit event for monitoring/metrics
    this.events.emit('request', { 
        type: 'completion', 
        model, 
        timestamp: new Date() 
    });
    
    // In a real implementation, this would call an AI model
    // Here we just echo back parts of the request with a mock response
    const response = {
        id: `mcp-resp-${Date.now()}`,
        model,
        text: `This is a response to: ${prompt.substring(0, 30)}...`,
        usage: {
        promptTokens: prompt.split(' ').length,
        completionTokens: 20,
        totalTokens: prompt.split(' ').length + 20
        }
    };
    
    // Simulate network delay
    await new Promise(resolve => setTimeout(resolve, 500));
    
    // Emit completion event
    this.events.emit('completion', {
        model,
        timestamp: new Date()
    });
    
    return {
        content: [
        {
            type: 'text',
            text: JSON.stringify(response)
        }
        ]
    };
    }
);

Install

Run the following command:

npm install

Run

npm start

Disclaimer:
This document has been translated using the AI translation service Co-op Translator. While we strive for accuracy, please be aware that automated translations may contain errors or inaccuracies. The original document in its native language should be considered the authoritative source. For critical information, professional human translation is recommended. We are not liable for any misunderstandings or misinterpretations arising from the use of this translation.