MCP Server Chart

Instructions

Implementation Reference

• src/server.ts:71-75 (handler)

  MCP generic tool execution handler that handles calls to 'generate_line_chart' by delegating to the callTool utility function.

  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);
  });

• src/server.ts:66-68 (registration)

  Registers 'generate_line_chart' tool in the MCP tools/list response via imported Charts.line.tool object.

  server.setRequestHandler(ListToolsRequestSchema, async () => ({
    tools: getEnabledTools().map((chart) => chart.tool),
  }));

• src/charts/line.ts:54-69 (schema)

  Defines the tool descriptor for 'generate_line_chart' including name, description, input schema (derived from Zod schema above), and annotations.

  // Line chart tool descriptor
  const tool = {
    name: "generate_line_chart",
    description:
      "Generate a line chart to show trends over time, such as, the ratio of Apple computer sales to Apple's profits changed from 2000 to 2016.",
    inputSchema: zodToJsonSchema(schema),
    annotations: {
      title: "Generate Line Chart",
      readOnlyHint: true,
    },
  };
  
  export const line = {
    schema,
    tool,
  };

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

  Dispatches 'generate_line_chart' to chartType 'line', validates args against line schema, generates and returns the chart URL for line charts.

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

  Helper function that generates the chart URL for 'line' type by sending POST request to the visualization service with chart config.

  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;
  }