MCP Server Chart

Instructions

Implementation Reference

• src/charts/sankey.ts:13-47 (schema)

  Zod schema defining the input parameters for the generate_sankey_chart tool, including data array, nodeAlign, style, theme, dimensions, and title.

  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,
  };

• src/charts/sankey.ts:49-63 (registration)

  Tool object registration with name, description, inputSchema (converted from Zod schema), and annotations for the generate_sankey_chart tool.

  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),
    annotations: {
      title: "Generate Sankey Chart",
      readOnlyHint: true,
    },
  };
  
  export const sankey = {
    schema,
    tool,
  };

• src/utils/callTool.ts:9-36 (helper)

  Mapping of tool name 'generate_sankey_chart' to internal chart type 'sankey' used in the handler.

  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/callTool.ts:44-111 (handler)

  Core handler function for all chart tools, including generate_sankey_chart: maps name to type, validates args against schema, generates chart URL via API, returns MCP content.

  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/server.ts:64-77 (registration)

  MCP server tool registration: ListTools returns tool definitions (including generate_sankey_chart), CallTool dispatches to callTool handler.

  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 that generates the chart URL by posting the chart type ('sankey') 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;
  }