n8n Workflow Builder MCP Server

Instructions

Implementation Reference

• src/index.ts:156-218 (handler)

  The CallToolRequestSchema request handler implements the core logic for the 'create_workflow' tool: it validates the input arguments, uses N8NWorkflowBuilder to construct the workflow with nodes and connections, and returns the exported JSON workflow.
  this.server.setRequestHandler(CallToolRequestSchema, async (request) => { if (request.params.name !== 'create_workflow') { throw new McpError(ErrorCode.MethodNotFound, `Unknown tool: ${request.params.name}`); } try { const builder = new N8NWorkflowBuilder(); function isWorkflowSpec(obj: any): obj is WorkflowSpec { return obj && typeof obj === 'object' && Array.isArray(obj.nodes) && obj.nodes.every((node: any) => typeof node === 'object' && typeof node.type === 'string' && typeof node.name === 'string' ) && (!obj.connections || ( Array.isArray(obj.connections) && obj.connections.every((conn: any) => typeof conn === 'object' && typeof conn.source === 'string' && typeof conn.target === 'string' ) )); } const args = request.params.arguments; if (!isWorkflowSpec(args)) { throw new McpError( ErrorCode.InvalidParams, 'Invalid workflow specification: must include nodes array with type and name properties' ); } const { nodes, connections } = args; for (const node of nodes) { builder.addNode(node.type, node.name, node.parameters || {}); } for (const conn of connections || []) { builder.connectNodes( conn.source, conn.target, conn.sourceOutput, conn.targetInput ); } return { content: [{ type: 'text', text: JSON.stringify(builder.exportWorkflow(), null, 2) }] }; } catch (error) { throw new McpError( ErrorCode.InternalError, `Workflow creation failed: ${error instanceof Error ? error.message : 'Unknown error'}` ); } });
• src/index.ts:105-135 (schema)

  Input schema for the 'create_workflow' tool, specifying the structure of nodes and optional connections.
  inputSchema: { type: 'object', properties: { nodes: { type: 'array', items: { type: 'object', properties: { type: { type: 'string' }, name: { type: 'string' }, parameters: { type: 'object' } }, required: ['type', 'name'] } }, connections: { type: 'array', items: { type: 'object', properties: { source: { type: 'string' }, target: { type: 'string' }, sourceOutput: { type: 'number', default: 0 }, targetInput: { type: 'number', default: 0 } }, required: ['source', 'target'] } } }, required: ['nodes'] }
• src/index.ts:102-137 (registration)

  Registration of the 'create_workflow' tool in the ListToolsRequestSchema handler.
  tools: [{ name: 'create_workflow', description: 'Create and configure n8n workflows programmatically', inputSchema: { type: 'object', properties: { nodes: { type: 'array', items: { type: 'object', properties: { type: { type: 'string' }, name: { type: 'string' }, parameters: { type: 'object' } }, required: ['type', 'name'] } }, connections: { type: 'array', items: { type: 'object', properties: { source: { type: 'string' }, target: { type: 'string' }, sourceOutput: { type: 'number', default: 0 }, targetInput: { type: 'number', default: 0 } }, required: ['source', 'target'] } } }, required: ['nodes'] } }] }));
• src/index.ts:11-77 (helper)

  Helper class N8NWorkflowBuilder that manages workflow nodes, connections, positioning, and exports the final n8n-compatible workflow JSON structure.
  class N8NWorkflowBuilder { private nodes: any[]; private connections: any[]; private nextPosition: { x: number, y: number }; constructor() { this.nodes = []; this.connections = []; this.nextPosition = { x: 100, y: 100 }; } addNode(nodeType: string, name: string, parameters: any) { const node = { type: nodeType, name: name, parameters: parameters, position: { ...this.nextPosition } }; this.nodes.push(node); this.nextPosition.x += 200; return name; } connectNodes(source: string, target: string, sourceOutput = 0, targetInput = 0) { this.connections.push({ source_node: source, target_node: target, source_output: sourceOutput, target_input: targetInput }); } exportWorkflow(): any { interface WorkflowConnection { node: string; type: string; index: number; sourceNode: string; sourceIndex: number; } interface Workflow { nodes: any[]; connections: { main: WorkflowConnection[]; }; } const workflow: Workflow = { nodes: this.nodes, connections: { main: [] } }; for (const conn of this.connections) { const connection: WorkflowConnection = { node: conn.target_node, type: 'main', index: conn.target_input, sourceNode: conn.source_node, sourceIndex: conn.source_output }; workflow.connections.main.push(connection); } return workflow; } }