MCP Server Chart

Instructions

Implementation Reference

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

  Core handler function for executing the generate_dual_axes_chart tool. Maps tool name to 'dual-axes' chart type (via CHART_TYPE_MAP), validates args against schema from Charts['dual-axes'], and generates chart 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/dual-axes.ts:16-81 (schema)

  Zod schema definitions for input validation of generate_dual_axes_chart, including DualAxesSeriesSchema and main schema. Also defines the tool descriptor with name, description, and inputSchema.

  const DualAxesSeriesSchema = z.object({
    type: z
      .enum(["column", "line"])
      .describe("The optional value can be 'column' or 'line'."),
    data: z
      .array(z.number())
      .describe(
        "When type is column, the data represents quantities, such as [91.9, 99.1, 101.6, 114.4, 121]. When type is line, the data represents ratios and its values are recommended to be less than 1, such as [0.055, 0.06, 0.062, 0.07, 0.075].",
      ),
    axisYTitle: z
      .string()
      .default("")
      .describe(
        "Set the y-axis title of the chart series, such as, axisYTitle: '销售额'.",
      )
      .optional(),
  });
  
  // Dual axes chart input schema
  const schema = {
    categories: z
      .array(z.string())
      .describe(
        "Categories for dual axes chart, such as, ['2015', '2016', '2017'].",
      )
      .nonempty({ message: "Dual axes chart categories cannot be empty." }),
    series: z
      .array(DualAxesSeriesSchema)
      .describe(
        "Series for dual axes chart, such as, [{ type: 'column', data: [91.9, 99.1, 101.6, 114.4, 121], axisYTitle: '销售额' }, { type: 'line', data: [0.055, 0.06, 0.062, 0.07, 0.075], 'axisYTitle': '利润率' }].",
      )
      .nonempty({ message: "Dual axes chart series cannot be empty." }),
    style: z
      .object({
        backgroundColor: BackgroundColorSchema,
        palette: PaletteSchema,
        startAtZero: StartAtZeroSchema,
        texture: TextureSchema,
      })
      .optional()
      .describe(
        "Style configuration for the chart with a JSON object, optional.",
      ),
    theme: ThemeSchema,
    width: WidthSchema,
    height: HeightSchema,
    title: TitleSchema,
    axisXTitle: AxisXTitleSchema,
  };
  
  // Dual axes chart tool descriptor
  const tool = {
    name: "generate_dual_axes_chart",
    description:
      "Generate a dual axes chart which is a combination chart that integrates two different chart types, typically combining a bar chart with a line chart to display both the trend and comparison of data, such as, the trend of sales and profit over time.",
    inputSchema: zodToJsonSchema(schema),
    annotations: {
      title: "Generate Dual Axes Chart",
      readOnlyHint: true,
    },
  };
  
  export const dualAxes = {
    schema,
    tool,
  };

• src/server.ts:64-77 (registration)

  Registers the MCP tool handlers. The listTools handler returns all enabled chart tools including generate_dual_axes_chart's tool descriptor. The callTool handler invokes the execution logic.

  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 names to internal chart types, specifically mapping 'generate_dual_axes_chart' to 'dual-axes' for dispatch.

  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/utils/generate.ts:12-39 (helper)

  Helper function that generates the chart URL by sending the chart type ('dual-axes') and options to the visualization server API.

  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;
  }