MCP Server Chart

Instructions

Implementation Reference

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

  The main handler function for all chart tools, including generate_pie_chart. Maps tool name to chartType 'pie', validates arguments using Charts.pie.schema, generates chart URL via generateChartUrl, and returns MCP content with the URL.
  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/pie.ts:50-59 (schema)

  Tool descriptor including name, description, inputSchema (converted from Zod schema), and annotations for generate_pie_chart.
  const tool = { name: "generate_pie_chart", description: "Generate a pie chart to show the proportion of parts, such as, market share and budget allocation.", inputSchema: zodToJsonSchema(schema), annotations: { title: "Generate Pie Chart", readOnlyHint: true, }, };
• src/charts/pie.ts:20-47 (schema)

  Zod-based input schema for generate_pie_chart tool parameters.
  const schema = { data: z .array(data) .describe( "Data for pie chart, it should be an array of objects, each object contains a `category` field and a `value` field, such as, [{ category: '分类一', value: 27 }].", ) .nonempty({ message: "Pie chart data cannot be empty." }), innerRadius: z .number() .default(0) .describe( "Set the innerRadius of pie chart, the value between 0 and 1. Set the pie chart as a donut chart. Set the value to 0.6 or number in [0 ,1] to enable it.", ), 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, };
• src/server.ts:64-77 (registration)

  Registers the MCP tool handlers. listTools returns array of all enabled chart.tool objects (including pie.tool for generate_pie_chart). callToolRequest handler dispatches to utils/callTool based on tool name.
  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 callTool to generate the chart URL by posting the chart type ('pie') and options to the visualization server.
  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; }