Klaviyo MCP Server

Implementation Reference

• src/tools/catalogs.js:12-24 (handler)

  The handler function that implements the core logic of the 'get_catalogs' tool. It fetches catalogs from the Klaviyo API using the klaviyoClient, formats the response as JSON string in MCP text content, and returns an error message if the request fails.

  async (params) => {
    try {
      const catalogs = await klaviyoClient.get('/catalogs/', params);
      return {
        content: [{ type: "text", text: JSON.stringify(catalogs, null, 2) }]
      };
    } catch (error) {
      return {
        content: [{ type: "text", text: `Error retrieving catalogs: ${error.message}` }],
        isError: true
      };
    }
  },

• src/tools/catalogs.js:8-11 (schema)

  Zod input schema defining optional pagination parameters (page_size, page_cursor) for the get_catalogs tool.

  {
    page_size: z.number().min(1).max(100).optional().describe("Number of catalogs per page (1-100)"),
    page_cursor: z.string().optional().describe("Cursor for pagination")
  },

• src/tools/catalogs.js:6-26 (registration)

  MCP server.tool call registering the 'get_catalogs' tool with name, schema, handler, and description 'Get catalogs from Klaviyo'.

  server.tool(
    "get_catalogs",
    {
      page_size: z.number().min(1).max(100).optional().describe("Number of catalogs per page (1-100)"),
      page_cursor: z.string().optional().describe("Cursor for pagination")
    },
    async (params) => {
      try {
        const catalogs = await klaviyoClient.get('/catalogs/', params);
        return {
          content: [{ type: "text", text: JSON.stringify(catalogs, null, 2) }]
        };
      } catch (error) {
        return {
          content: [{ type: "text", text: `Error retrieving catalogs: ${error.message}` }],
          isError: true
        };
      }
    },
    { description: "Get catalogs from Klaviyo" }
  );

• src/server.js:41-41 (registration)

  Invocation of registerCatalogTools(server) which performs the tool registrations including get_catalogs.

  registerCatalogTools(server);

• src/klaviyo-client.js:135-180 (helper)

  klaviyoClient.get function called from the handler; implements API GET requests to Klaviyo with pagination support, caching, rate limit retries, backoff, and detailed error handling.

  export async function get(endpoint, params = {}, fallbackFn) {
    // Build the URL with query parameters according to Klaviyo API specs
    let url = endpoint;
    const queryParams = [];
    
    // Special handling for campaign endpoint - add required filter if missing
    if (endpoint === '/campaigns/' && !params.filter) {
      logger.debug('Adding default email filter for campaigns endpoint');
      params.filter = "equals(messages.channel,'email')";
    }
    
    // Handle filter parameter if provided
    if (params.filter) {
      queryParams.push(`filter=${encodeURIComponent(params.filter)}`);
    }
    
    // Handle include parameter if provided
    if (params.include) {
      queryParams.push(`include=${encodeURIComponent(params.include)}`);
    }
    
    // Handle page_size parameter if provided
    if (params.page_size) {
      queryParams.push(`page[size]=${params.page_size}`);
    }
    
    // Handle pagination cursor if provided
    if (params.page_cursor) {
      queryParams.push(`page[cursor]=${params.page_cursor}`);
    }
    
    // Add query parameters to URL
    if (queryParams.length > 0) {
      url = `${endpoint}?${queryParams.join('&')}`;
    }
    
    logger.debug(`Prepared GET request to: ${url}`);
    
    return executeWithRetry(
      () => client.get(url),
      'GET',
      endpoint,
      params,
      fallbackFn
    );
  }