MCP Server Chart

Instructions

Implementation Reference

• src/utils/callTool.ts:44-111 (handler)

  Core handler function that executes the generate_waterfall_chart tool. Maps tool name to 'waterfall' chart type, validates input schema, generates chart URL via external service, and returns the result.
  export async function callTool(tool: string, args: object = {}) { logger.info(`Calling tool: ${tool}`); const chartType = CHART_TYPE_MAP[tool as keyof typeof CHART_TYPE_MAP]; if (!chartType) { logger.error(`Unknown tool: ${tool}`); throw new McpError(ErrorCode.MethodNotFound, `Unknown tool: ${tool}.`); } try { // Validate input using Zod before sending to API. // Select the appropriate schema based on the chart type. const schema = Charts[chartType].schema; if (schema) { // Use safeParse instead of parse and try-catch. const result = z.object(schema).safeParse(args); if (!result.success) { logger.error(`Invalid parameters: ${result.error.message}`); throw new McpError( ErrorCode.InvalidParams, `Invalid parameters: ${result.error.message}`, ); } } const isMapChartTool = [ "generate_district_map", "generate_path_map", "generate_pin_map", ].includes(tool); if (isMapChartTool) { // For map charts, we use the generateMap function, and return the mcp result. const { metadata, ...result } = await generateMap(tool, args); return result; } const url = await generateChartUrl(chartType, args); logger.info(`Generated chart URL: ${url}`); return { content: [ { type: "text", text: url, }, ], _meta: { description: "This is the chart's spec and configuration, which can be renderred to corresponding chart by AntV GPT-Vis chart components.", spec: { type: chartType, ...args }, }, }; // biome-ignore lint/suspicious/noExplicitAny: <explanation> } catch (error: any) { logger.error( `Failed to generate chart: ${error.message || "Unknown error"}.`, ); if (error instanceof McpError) throw error; if (error instanceof ValidateError) throw new McpError(ErrorCode.InvalidParams, error.message); throw new McpError( ErrorCode.InternalError, `Failed to generate chart: ${error?.message || "Unknown error."}`, ); } }
• src/charts/waterfall.ts:36-80 (schema)

  Input schema (Zod) for validating arguments to generate_waterfall_chart, including data array with categories, values, totals, and styling options.
  const schema = { data: z .array(data) .describe( "Data for waterfall chart, it should be an array of objects. Each object must contain a `category` field. For regular items, a `value` field is also required. The `isIntermediateTotal` field marks intermediate subtotals, and the `isTotal` field marks the final total. For example, [{ category: 'Initial', value: 100 }, { category: 'Increase', value: 50 }, { category: 'Subtotal', isIntermediateTotal: true }, { category: 'Decrease', value: -30 }, { category: 'Total', isTotal: true }].", ) .nonempty({ message: "Waterfall chart data cannot be empty." }), style: z .object({ backgroundColor: BackgroundColorSchema, texture: TextureSchema, palette: z .object({ positiveColor: z .string() .optional() .describe( "Color for positive values (increases). Default is '#FF4D4F'.", ), negativeColor: z .string() .optional() .describe( "Color for negative values (decreases). Default is '#2EBB59'.", ), totalColor: z .string() .optional() .describe( "Color for total and intermediate total bars. Default is '#1783FF'.", ), }) .optional(), }) .optional() .describe( "Style configuration for the chart with a JSON object, optional.", ), theme: ThemeSchema, width: WidthSchema, height: HeightSchema, title: TitleSchema, axisXTitle: AxisXTitleSchema, axisYTitle: AxisYTitleSchema, };
• src/server.ts:64-77 (registration)

  Registers the MCP handlers for tools/list (includes generate_waterfall_chart descriptor from Charts.waterfall.tool) and tools/call (invokes generic callTool handler).
  function setupToolHandlers(server: Server): void { logger.info("setting up tool handlers..."); server.setRequestHandler(ListToolsRequestSchema, async () => ({ tools: getEnabledTools().map((chart) => chart.tool), })); // biome-ignore lint/suspicious/noExplicitAny: <explanation> server.setRequestHandler(CallToolRequestSchema, async (request: any) => { logger.info("calling tool", request.params.name, request.params.arguments); return await callTool(request.params.name, request.params.arguments); }); logger.info("tool handlers set up"); }
• src/utils/callTool.ts:9-36 (helper)

  Mapping from tool name 'generate_waterfall_chart' to internal chart type 'waterfall' used by the handler.
  const CHART_TYPE_MAP = { generate_area_chart: "area", generate_bar_chart: "bar", generate_boxplot_chart: "boxplot", generate_column_chart: "column", generate_district_map: "district-map", generate_dual_axes_chart: "dual-axes", generate_fishbone_diagram: "fishbone-diagram", generate_flow_diagram: "flow-diagram", generate_funnel_chart: "funnel", generate_histogram_chart: "histogram", generate_line_chart: "line", generate_liquid_chart: "liquid", generate_mind_map: "mind-map", generate_network_graph: "network-graph", generate_organization_chart: "organization-chart", generate_path_map: "path-map", generate_pie_chart: "pie", generate_pin_map: "pin-map", generate_radar_chart: "radar", generate_sankey_chart: "sankey", generate_scatter_chart: "scatter", generate_treemap_chart: "treemap", generate_venn_chart: "venn", generate_violin_chart: "violin", generate_waterfall_chart: "waterfall", generate_word_cloud_chart: "word-cloud", } as const;
• src/charts/waterfall.ts:83-92 (helper)

  Tool descriptor defining name, description, input schema, and annotations for registration in MCP tools/list.
  const tool = { name: "generate_waterfall_chart", description: "Generate a waterfall chart to visualize the cumulative effect of sequentially introduced positive or negative values, such as showing how an initial value is affected by a series of intermediate positive or negative values leading to a final result. Waterfall charts are ideal for financial analysis, budget tracking, profit and loss statements, and understanding the composition of changes over time or categories.", inputSchema: zodToJsonSchema(schema), annotations: { title: "Generate Waterfall Chart", readOnlyHint: true, }, };