MCP Server Chart

Instructions

Implementation Reference

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

  The core handler function for executing generate_liquid_chart and all chart tools. Maps 'generate_liquid_chart' to 'liquid', validates args with Charts.liquid.schema, generates chart URL via generateChartUrl, and returns MCP tool 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/liquid.ts:12-53 (schema)

  Input schema definition using Zod for generate_liquid_chart parameters (percent, shape, style, theme, dimensions, title) and tool metadata with inputSchema converted to JSON schema.
  const schema = { percent: z .number() .describe( "The percentage value to display in the liquid chart, should be a number between 0 and 1, where 1 represents 100%. For example, 0.75 represents 75%.", ) .min(0, { message: "Value must be at least 0." }) .max(1, { message: "Value must be at most 1." }), shape: z .enum(["circle", "rect", "pin", "triangle"]) .optional() .default("circle") .describe( "The shape of the liquid chart, can be 'circle', 'rect', 'pin', or 'triangle'. Default is 'circle'.", ), style: z .object({ backgroundColor: BackgroundColorSchema, texture: TextureSchema, color: z .string() .optional() .describe( "Custom color for the liquid chart, if not specified, defaults to the theme color.", ), }) .optional() .describe( "Style configuration for the chart with a JSON object, optional.", ), theme: ThemeSchema, width: WidthSchema, height: HeightSchema, title: TitleSchema, }; const tool = { name: "generate_liquid_chart", description: "Generate a liquid chart to visualize a single value as a percentage, such as, the current occupancy rate of a reservoir or the completion percentage of a project.", inputSchema: zodToJsonSchema(schema), };
• src/server.ts:64-77 (registration)

  Registers the tool handlers on the MCP server: ListTools returns metadata/schemas for enabled tools including generate_liquid_chart (from Charts.liquid.tool), and CallTool invokes callTool by 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/callTool.ts:9-35 (helper)

  Static mapping from tool name 'generate_liquid_chart' to internal chart type 'liquid' used in callTool.
  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_word_cloud_chart: "word-cloud", } as const;
• src/utils/generate.ts:12-39 (helper)

  Helper function called by callTool to generate the chart image URL by sending POST request with type='liquid' and options to the external 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; }