MCP Utility Tools

Instructions

Implementation Reference

• src/index.ts:268-303 (handler)

  The handler for the 'cache_get' tool. It retrieves the cache entry by key, checks if it exists and is not expired, and returns a JSON response with the value or indication if not found or expired.

  case "cache_get": {
    const { key } = args as { key: string };
    
    const entry = cache.get(key);
    if (!entry) {
      return {
        content: [{
          type: "text",
          text: JSON.stringify({ found: false, key })
        }]
      };
    }
  
    // Check if expired
    if (entry.expiresAt <= Date.now()) {
      cache.delete(key);
      return {
        content: [{
          type: "text",
          text: JSON.stringify({ found: false, key, reason: "expired" })
        }]
      };
    }
  
    return {
      content: [{
        type: "text",
        text: JSON.stringify({
          found: true,
          key,
          value: entry.value,
          expires_in_seconds: Math.floor((entry.expiresAt - Date.now()) / 1000)
        })
      }]
    };
  }

• src/index.ts:84-97 (registration)

  The tool registration object in the tools array, which includes the name, description, and input schema. This is returned by the ListTools handler.

  {
    name: "cache_get",
    description: "Get a value from the cache by key",
    inputSchema: {
      type: "object",
      properties: {
        key: {
          type: "string",
          description: "Cache key to retrieve"
        }
      },
      required: ["key"]
    }
  },

• src/index.ts:87-96 (schema)

  The input schema defining the expected arguments for the cache_get tool: a required 'key' string.

  inputSchema: {
    type: "object",
    properties: {
      key: {
        type: "string",
        description: "Cache key to retrieve"
      }
    },
    required: ["key"]
  }

• src/index.ts:13-18 (helper)

  The CacheEntry interface and cache Map storage used by the cache_get handler and other cache tools.

  interface CacheEntry {
    value: any;
    expiresAt: number;
  }
  
  const cache = new Map<string, CacheEntry>();