MCP Server Chart

Instructions

Implementation Reference

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

  The callTool function is the core handler for executing the generate_flow_diagram tool. It maps 'generate_flow_diagram' to chart type 'flow-diagram' (via CHART_TYPE_MAP), validates arguments against the tool's schema, generates the chart URL using generateChartUrl, and returns the result in MCP format.
  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/flow-diagram.ts:14-40 (schema)

  Defines the Zod input schema for the generate_flow_diagram tool, specifying required data structure (nodes and edges), optional style, theme, width, and height.
  const schema = { data: z .object({ nodes: z .array(NodeSchema) .nonempty({ message: "At least one node is required." }), edges: z.array(EdgeSchema), }) .describe( "Data for flow diagram chart, such as, { nodes: [{ name: 'node1' }, { name: 'node2' }], edges: [{ source: 'node1', target: 'node2', name: 'edge1' }] }.", ) .refine(validatedNodeEdgeDataSchema, { message: "Invalid parameters", path: ["data", "edges"], }), style: z .object({ texture: TextureSchema, }) .optional() .describe( "Style configuration for the chart with a JSON object, optional.", ), theme: ThemeSchema, width: WidthSchema, height: HeightSchema, };
• src/charts/flow-diagram.ts:43-48 (registration)

  Tool descriptor object defining the name 'generate_flow_diagram', description, and JSON schema for input, used in MCP tool listing.
  const tool = { name: "generate_flow_diagram", description: "Generate a flow diagram chart to show the steps and decision points of a process or system, such as, scenarios requiring linear process presentation.", inputSchema: zodToJsonSchema(schema), };
• src/server.ts:64-77 (registration)

  Registers the MCP ListTools and CallTool request handlers. ListTools returns all enabled chart tools (including generate_flow_diagram via Charts exports), and CallTool delegates to callTool function.
  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 called by the handler to generate the actual flow diagram chart by sending the spec (type: 'flow-diagram', options) to the visualization server API and returning the rendered chart URL.
  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; }