MCP Server Chart

Instructions

Implementation Reference

• src/utils/callTool.ts:43-110 (handler)

  Generic handler for the generate_sankey_chart tool (and all chart tools). Maps 'generate_sankey_chart' to chart type 'sankey' at line 29, validates arguments using the sankey schema, and calls generateChartUrl to produce the chart.
  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/sankey.ts:13-54 (schema)

  Zod-based input schema and tool metadata (name, description, inputSchema) for generate_sankey_chart.
  const data = z.object({ source: z.string(), target: z.string(), value: z.number(), }); const schema = { data: z .array(data) .describe( "Date for sankey chart, such as, [{ source: 'Landing Page', target: 'Product Page', value: 50000 }, { source: 'Product Page', target: 'Add to Cart', value: 35000 }, { source: 'Add to Cart', target: 'Checkout', value: 25000 }, { source: 'Checkout', target: 'Payment', value: 15000 }, { source: 'Payment', target: 'Purchase Completed', value: 8000 }].", ) .nonempty({ message: "Sankey chart data cannot be empty." }), nodeAlign: z .enum(["left", "right", "justify", "center"]) .optional() .default("center") .describe( "Alignment of nodes in the sankey chart, such as, 'left', 'right', 'justify', or 'center'.", ), style: z .object({ backgroundColor: BackgroundColorSchema, palette: PaletteSchema, texture: TextureSchema, }) .optional() .describe( "Style configuration for the chart with a JSON object, optional.", ), theme: ThemeSchema, width: WidthSchema, height: HeightSchema, title: TitleSchema, }; const tool = { name: "generate_sankey_chart", description: "Generate a sankey chart to visualize the flow of data between different stages or categories, such as, the user journey from landing on a page to completing a purchase.", inputSchema: zodToJsonSchema(schema), };
• src/server.ts:64-77 (registration)

  MCP server tool handler setup. listTools dynamically includes generate_sankey_chart from Charts.sankey.tool (via getEnabledTools()), and tools/call requests are dispatched to callTool with the tool name and arguments.
  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/generate.ts:12-39 (helper)

  Helper function called by the handler to POST the chart type ('sankey') and configuration to an external visualization server, returning the rendered chart URL.
  export async function generateChartUrl( type: string, // biome-ignore lint/suspicious/noExplicitAny: <explanation> options: Record<string, any>, ): Promise<string> { const url = getVisRequestServer(); const response = await axios.post( url, { type, ...options, source: "mcp-server-chart", }, { headers: { "Content-Type": "application/json", }, }, ); const { success, errorMessage, resultObj } = response.data; if (!success) { throw new Error(errorMessage); } return resultObj; }