vchart-mcp-server

Instructions

Implementation Reference

• src/server.ts:43-125 (handler)

  Generic MCP CallTool handler that dispatches to generateChartByType based on tool name matching 'generate_scatter_chart' to chartType 'scatter'. Validates input with scatter schema and returns image/html/spec.
  server.setRequestHandler(CallToolRequestSchema, async request => { const toolName = request.params.name; const chartType = Object.keys(Charts).find( key => (Charts as any)[key].tool.name === toolName ); if (!chartType) { throw new McpError( ErrorCode.MethodNotFound, `Unknown tool: ${request.params.name}.` ); } try { // Validate input using Zod before generating chart const args = request.params.arguments || {}; // Select the appropriate schema based on the chart type const schema = Charts[chartType as keyof typeof Charts].schema; if (schema) { const result = schema.safeParse(args); if (!result.success) { throw new McpError( ErrorCode.InvalidParams, `Invalid parameters: ${result.error.message}` ); } } const res = await generateChartByType(chartType, args); if (res && (res as any).spec) { return { content: [ { type: 'text', text: JSON.stringify((res as any).spec, null, 2), }, ], }; } if (res && (res as any).image) { return { content: [ { type: 'text', text: (res as any).image, }, ], }; } if (res && (res as any).html) { return { content: [ { type: 'text', text: (res as any).html, }, ], }; } return { content: [ { type: 'text', text: 'Failed to generate chart', }, ], }; } catch (error: any) { if (error instanceof McpError) { throw error; } throw new McpError( ErrorCode.InternalError, `Failed to generate chart: ${error?.message || 'Unknown error.'}` ); } });
• src/charts/scatter.ts:29-63 (schema)

  Zod schema defining the input parameters and validation for the generate_scatter_chart tool, including dataTable, xField, yField, etc.
  const schema = z.object({ output: ChartOutputSchema, width: WidthSchema, height: HeightSchema, dataTable: z .array(z.any()) .describe("Scatter chart data, e.g., [{ x: 34, y: 10, category: 'A' }].") .nonempty({ message: 'Scatter chart data cannot be empty.' }), xField: YFieldSchema, yField: YFieldSchema, sizeField: z.string().optional().describe('Numeric field for bubble size.'), colorField: ColorFieldSchema, chartTheme: ThemeSchema, title: TitleTextSchema, subTitle: TitleSubTextSchema, titleOrient: TitleOrientSchema, xAxisType: XAxisTypeSchema, xAxisOrient: XAxisOrientSchema, xAxisTitle: XAxisTitleSchema, xAxisHasGrid: XAxisHasGridSchema, xAxisHasLabel: XAxisHasLabelSchema, xAxisHasTick: XAxisHasTickSchema, yAxisType: YAxisTypeSchema, yAxisOrient: YAxisOrientSchema, yAxisTitle: YAxisTitleSchema, yAxisHasGrid: YAxisHasGridSchema, yAxisHasLabel: YAxisHasLabelSchema, yAxisHasTick: YAxisHasTickSchema, background: BackgroundSchema, colors: ColorsSchema, });
• src/server.ts:34-38 (registration)

  Registers the generate_scatter_chart tool by including it in the list of tools returned for ListToolsRequest, sourced from Charts.scatter.tool.
  server.setRequestHandler(ListToolsRequestSchema, async () => { return { tools: Object.values(Charts).map(chart => (chart as any).tool), }; });
• src/charts/scatter.ts:65-75 (registration)

  Defines the tool metadata (name, description, schema) exported as scatter.tool, which is imported and listed in the MCP server.
  const tool = { name: 'generate_scatter_chart', description: 'Generate a scatter chart to visually display the distribution, clustering trends, and correlations of data points in two-dimensional or multi-dimensional space. Suitable for analyzing relationships between variables, outlier detection, and similar scenarios.', inputSchema: convertZodToJsonSchema(schema), }; export const scatter = { schema, tool, };
• src/utils/generateChart.ts:42-202 (helper)

  Helper function that implements the chart generation logic for 'scatter' type: normalizes options, extracts fields (xField, yField, sizeField, colorField), generates VChart spec, and produces image/html/spec output.
  export async function generateChartByType(chartType: string, options: any) { const { title, subTitle, titleOrient, xAxisType, xAxisOrient, xAxisTitle, xAxisHasGrid, xAxisHasLabel, xAxisHasTick, yAxisType, yAxisOrient, yAxisTitle, yAxisHasGrid, yAxisHasLabel, yAxisHasTick, leftYAxisTitle, leftYAxisHasGrid, leftYAxisHasLabel, leftYAxisHasTick, rightYAxisTitle, rightYAxisHasGrid, rightYAxisHasLabel, rightYAxisHasTick, angleAxisTitle, angleAxisHasGrid, angleAxisHasLabel, angleAxisHasTick, angleAxisType, radiusAxisHasGrid, radiusAxisHasLabel, radiusAxisHasTick, radiusAxisType, radiusAxisTitle, output, width, height, ...res } = options; const opts = { ...res }; const titleObj = filterValidAttributes({ text: title, subText: subTitle, orient: titleOrient, }); const xAxisObj = filterValidAttributes({ type: xAxisType, orient: xAxisOrient, title: xAxisTitle, hasGrid: xAxisHasGrid, hasLabel: xAxisHasLabel, hasTick: xAxisHasTick, }); const yAxisObj = filterValidAttributes({ type: yAxisType, orient: yAxisOrient, title: yAxisTitle, hasGrid: yAxisHasGrid, hasLabel: yAxisHasLabel, hasTick: yAxisHasTick, }); const leftYAxisObj = filterValidAttributes({ title: leftYAxisTitle, hasGrid: leftYAxisHasGrid, hasLabel: leftYAxisHasLabel, hasTick: leftYAxisHasTick, }); const rightYAxisObj = filterValidAttributes({ title: rightYAxisTitle, hasGrid: rightYAxisHasGrid, hasLabel: rightYAxisHasLabel, hasTick: rightYAxisHasTick, }); const angleAxisObj = filterValidAttributes({ title: angleAxisTitle, hasGrid: angleAxisHasGrid, hasLabel: angleAxisHasLabel, hasTick: angleAxisHasTick, type: angleAxisType, }); const radiusAxisObj = filterValidAttributes({ hasGrid: radiusAxisHasGrid, hasLabel: radiusAxisHasLabel, hasTick: radiusAxisHasTick, type: radiusAxisType, title: radiusAxisTitle, }); const cell: Record<string, string> = {}; [ "xField", "yField", "colorField", "categoryField", "valueField", "wordField", "sizeField", "timeField", "sourceField", "targetField", "setsField", "radiusField", ].forEach((fieldName) => { if (isValid(options[fieldName])) { cell[fieldName.replace("Field", "")] = options[fieldName]; delete opts[fieldName]; } }); opts.cell = cell; if (!isEmpty(titleObj)) { opts.title = titleObj; } const axes = [ xAxisObj, yAxisObj, leftYAxisObj, rightYAxisObj, angleAxisObj, radiusAxisObj, ]; if (axes.some((axis) => !isEmpty(axis))) { opts.axes = axes.filter((axis) => !isEmpty(axis)); } const { spec } = generateChart(options.chartType ?? chartType, opts); if (!spec) { return null; } if (output === "spec") { if (isValid(width)) { spec.width = width; } if (isValid(height)) { spec.height = height; } return { spec: spec, }; } return gentrateChartImageOrHtml(output, spec, { width: `${width ?? 500}px`, height: `${height ?? 500}px`, }); }