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packages/@n8n/nodes-langchain/nodes/mcp/McpClientTool/McpClientTool.node.ts

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+import { CallToolResultSchema } from '@modelcontextprotocol/sdk/types.js';
+import { StructuredToolkit } from 'n8n-core';
+import {
+	type IDataObject,
+	type IExecuteFunctions,
+	type INodeExecutionData,
+	NodeConnectionTypes,
+	NodeOperationError,
+	type INodeType,
+	type INodeTypeDescription,
+	type ISupplyDataFunctions,
+	type SupplyData,
+} from 'n8n-workflow';
+
+import { logWrapper, getConnectionHintNoticeField } from '@n8n/ai-utilities';
+
+import { getTools } from './loadOptions';
+import type { McpToolIncludeMode } from './types';
+import { createCallTool, getSelectedTools, mcpToolToDynamicTool } from './utils';
+import { credentials, transportSelect } from '../shared/descriptions';
+import type { McpAuthenticationOption, McpServerTransport } from '../shared/types';
+import {
+	connectMcpClient,
+	getAllTools,
+	getAuthHeaders,
+	mapToNodeOperationError,
+	tryRefreshOAuth2Token,
+} from '../shared/utils';
+import type { JSONSchema7 } from 'json-schema';
+import pick from 'lodash/pick';
+
+/**
+ * Get node parameters for MCP client configuration
+ */
+function getNodeConfig(
+	ctx: ISupplyDataFunctions | IExecuteFunctions,
+	itemIndex: number,
+): {
+	authentication: McpAuthenticationOption;
+	timeout: number;
+	serverTransport: McpServerTransport;
+	endpointUrl: string;
+	mode: McpToolIncludeMode;
+	includeTools: string[];
+	excludeTools: string[];
+} {
+	const node = ctx.getNode();
+	const authentication = ctx.getNodeParameter(
+		'authentication',
+		itemIndex,
+	) as McpAuthenticationOption;
+	const timeout = ctx.getNodeParameter('options.timeout', itemIndex, 60000) as number;
+
+	let serverTransport: McpServerTransport;
+	let endpointUrl: string;
+	if (node.typeVersion === 1) {
+		serverTransport = 'sse';
+		endpointUrl = ctx.getNodeParameter('sseEndpoint', itemIndex) as string;
+	} else {
+		serverTransport = ctx.getNodeParameter('serverTransport', itemIndex) as McpServerTransport;
+		endpointUrl = ctx.getNodeParameter('endpointUrl', itemIndex) as string;
+	}
+
+	const mode = ctx.getNodeParameter('include', itemIndex) as McpToolIncludeMode;
+	const includeTools = ctx.getNodeParameter('includeTools', itemIndex, []) as string[];
+	const excludeTools = ctx.getNodeParameter('excludeTools', itemIndex, []) as string[];
+
+	return {
+		authentication,
+		timeout,
+		serverTransport,
+		endpointUrl,
+		mode,
+		includeTools,
+		excludeTools,
+	};
+}
+
+/**
+ * Connect to MCP server and get filtered tools
+ */
+async function connectAndGetTools(
+	ctx: ISupplyDataFunctions | IExecuteFunctions,
+	config: ReturnType<typeof getNodeConfig>,
+) {
+	const node = ctx.getNode();
+	const { headers } = await getAuthHeaders(ctx, config.authentication);
+
+	const client = await connectMcpClient({
+		serverTransport: config.serverTransport,
+		endpointUrl: config.endpointUrl,
+		headers,
+		name: node.type,
+		version: node.typeVersion,
+		onUnauthorized: async (headers) =>
+			await tryRefreshOAuth2Token(ctx, config.authentication, headers),
+	});
+
+	if (!client.ok) {
+		return { client, mcpTools: null, error: client.error };
+	}
+
+	const allTools = await getAllTools(client.result);
+	const mcpTools = getSelectedTools({
+		tools: allTools,
+		mode: config.mode,
+		includeTools: config.includeTools,
+		excludeTools: config.excludeTools,
+	});
+
+	return { client: client.result, mcpTools, error: null };
+}
+
+export class McpClientTool implements INodeType {
+	description: INodeTypeDescription = {
+		displayName: 'MCP Client Tool',
+		name: 'mcpClientTool',
+		icon: {
+			light: 'file:../mcp.svg',
+			dark: 'file:../mcp.dark.svg',
+		},
+		group: ['output'],
+		version: [1, 1.1, 1.2],
+		description: 'Connect tools from an MCP Server',
+		defaults: {
+			name: 'MCP Client',
+		},
+		codex: {
+			categories: ['AI'],
+			subcategories: {
+				AI: ['Tools'],
+				Tools: ['Recommended Tools'],
+			},
+			alias: ['Model Context Protocol', 'MCP Client'],
+			resources: {
+				primaryDocumentation: [
+					{
+						url: 'https://docs.n8n.io/integrations/builtin/cluster-nodes/sub-nodes/n8n-nodes-langchain.toolmcp/',
+					},
+				],
+			},
+		},
+		inputs: [],
+		outputs: [{ type: NodeConnectionTypes.AiTool, displayName: 'Tools' }],
+		credentials,
+		properties: [
+			getConnectionHintNoticeField([NodeConnectionTypes.AiAgent]),
+			{
+				displayName: 'SSE Endpoint',
+				name: 'sseEndpoint',
+				type: 'string',
+				description: 'SSE Endpoint of your MCP server',
+				placeholder: 'e.g. https://my-mcp-server.ai/sse',
+				default: '',
+				required: true,
+				displayOptions: {
+					show: {
+						'@version': [1],
+					},
+				},
+			},
+			{
+				displayName: 'Endpoint',
+				name: 'endpointUrl',
+				type: 'string',
+				description: 'Endpoint of your MCP server',
+				placeholder: 'e.g. https://my-mcp-server.ai/mcp',
+				default: '',
+				required: true,
+				displayOptions: {
+					show: {
+						'@version': [{ _cnd: { gte: 1.1 } }],
+					},
+				},
+			},
+			transportSelect({
+				defaultOption: 'sse',
+				displayOptions: {
+					show: {
+						'@version': [1.1],
+					},
+				},
+			}),
+			transportSelect({
+				defaultOption: 'httpStreamable',
+				displayOptions: {
+					show: {
+						'@version': [{ _cnd: { gte: 1.2 } }],
+					},
+				},
+			}),
+			{
+				displayName: 'Authentication',
+				name: 'authentication',
+				type: 'options',
+				options: [
+					{
+						name: 'Bearer Auth',
+						value: 'bearerAuth',
+					},
+					{
+						name: 'Header Auth',
+						value: 'headerAuth',
+					},
+					{
+						name: 'None',
+						value: 'none',
+					},
+				],
+				default: 'none',
+				description: 'The way to authenticate with your endpoint',
+				displayOptions: {
+					show: {
+						'@version': [{ _cnd: { lt: 1.2 } }],
+					},
+				},
+			},
+			{
+				displayName: 'Authentication',
+				name: 'authentication',
+				type: 'options',
+				options: [
+					{
+						name: 'Bearer Auth',
+						value: 'bearerAuth',
+					},
+					{
+						name: 'Header Auth',
+						value: 'headerAuth',
+					},
+					{
+						name: 'MCP OAuth2',
+						value: 'mcpOAuth2Api',
+					},
+					{
+						name: 'Multiple Headers Auth',
+						value: 'multipleHeadersAuth',
+					},
+					{
+						name: 'None',
+						value: 'none',
+					},
+				],
+				default: 'none',
+				description: 'The way to authenticate with your endpoint',
+				displayOptions: {
+					show: {
+						'@version': [{ _cnd: { gte: 1.2 } }],
+					},
+				},
+			},
+			{
+				displayName: 'Credentials',
+				name: 'credentials',
+				type: 'credentials',
+				default: '',
+				displayOptions: {
+					show: {
+						authentication: ['headerAuth', 'bearerAuth', 'mcpOAuth2Api', 'multipleHeadersAuth'],
+					},
+				},
+			},
+			{
+				displayName: 'Tools to Include',
+				name: 'include',
+				type: 'options',
+				description: 'How to select the tools you want to be exposed to the AI Agent',
+				default: 'all',
+				options: [
+					{
+						name: 'All',
+						value: 'all',
+						description: 'Also include all unchanged fields from the input',
+					},
+					{
+						name: 'Selected',
+						value: 'selected',
+						description: 'Also include the tools listed in the parameter "Tools to Include"',
+					},
+					{
+						name: 'All Except',
+						value: 'except',
+						description: 'Exclude the tools listed in the parameter "Tools to Exclude"',
+					},
+				],
+			},
+			{
+				displayName: 'Tools to Include',
+				name: 'includeTools',
+				type: 'multiOptions',
+				default: [],
+				description:
+					'Choose from the list, or specify IDs using an <a href="https://docs.n8n.io/code/expressions/">expression</a>',
+				typeOptions: {
+					loadOptionsMethod: 'getTools',
+					loadOptionsDependsOn: ['sseEndpoint'],
+				},
+				displayOptions: {
+					show: {
+						include: ['selected'],
+					},
+				},
+			},
+			{
+				displayName: 'Tools to Exclude',
+				name: 'excludeTools',
+				type: 'multiOptions',
+				default: [],
+				description:
+					'Choose from the list, or specify IDs using an <a href="https://docs.n8n.io/code/expressions/">expression</a>',
+				typeOptions: {
+					loadOptionsMethod: 'getTools',
+				},
+				displayOptions: {
+					show: {
+						include: ['except'],
+					},
+				},
+			},
+			{
+				displayName: 'Options',
+				name: 'options',
+				placeholder: 'Add Option',
+				description: 'Additional options to add',
+				type: 'collection',
+				default: {},
+				options: [
+					{
+						displayName: 'Timeout',
+						name: 'timeout',
+						type: 'number',
+						typeOptions: {
+							minValue: 1,
+						},
+						default: 60000,
+						description: 'Time in ms to wait for tool calls to finish',
+					},
+				],
+			},
+		],
+	};
+
+	methods = {
+		loadOptions: {
+			getTools,
+		},
+	};
+
+	async supplyData(this: ISupplyDataFunctions, itemIndex: number): Promise<SupplyData> {
+		const node = this.getNode();
+		const config = getNodeConfig(this, itemIndex);
+
+		const setError = (error: NodeOperationError): SupplyData => {
+			this.addOutputData(NodeConnectionTypes.AiTool, itemIndex, error);
+			throw error;
+		};
+
+		const { client, mcpTools, error } = await connectAndGetTools(this, config);
+
+		if (error) {
+			this.logger.error('McpClientTool: Failed to connect to MCP Server', { error });
+			return setError(mapToNodeOperationError(node, error));
+		}
+
+		this.logger.debug('McpClientTool: Successfully connected to MCP Server');
+
+		if (!mcpTools?.length) {
+			return setError(
+				new NodeOperationError(node, 'MCP Server returned no tools', {
+					itemIndex,
+					description:
+						'Connected successfully to your MCP server but it returned an empty list of tools.',
+				}),
+			);
+		}
+
+		const tools = mcpTools.map((tool) =>
+			logWrapper(
+				mcpToolToDynamicTool(
+					tool,
+					createCallTool(tool.name, client, config.timeout, (errorMessage) => {
+						const error = new NodeOperationError(node, errorMessage, { itemIndex });
+						void this.addOutputData(NodeConnectionTypes.AiTool, itemIndex, error);
+						this.logger.error(`McpClientTool: Tool "${tool.name}" failed to execute`, { error });
+					}),
+				),
+				this,
+			),
+		);
+
+		this.logger.debug(`McpClientTool: Connected to MCP Server with ${tools.length} tools`);
+
+		const toolkit = new StructuredToolkit(tools);
+
+		return { response: toolkit, closeFunction: async () => await client.close() };
+	}
+
+	async execute(this: IExecuteFunctions): Promise<INodeExecutionData[][]> {
+		const node = this.getNode();
+		const items = this.getInputData();
+		const returnData: INodeExecutionData[] = [];
+
+		for (let itemIndex = 0; itemIndex < items.length; itemIndex++) {
+			const item = items[itemIndex];
+			const config = getNodeConfig(this, itemIndex);
+
+			const { client, mcpTools, error } = await connectAndGetTools(this, config);
+
+			if (error) {
+				throw new NodeOperationError(node, error.error, { itemIndex });
+			}
+
+			if (!mcpTools?.length) {
+				throw new NodeOperationError(node, 'MCP Server returned no tools', { itemIndex });
+			}
+
+			for (const tool of mcpTools) {
+				// Check for tool name in item.json.tool (for toolkit execution from agent)
+				// or item.tool (for direct execution)
+				if (!item.json.tool || typeof item.json.tool !== 'string') {
+					throw new NodeOperationError(node, 'Tool name not found in item.json.tool or item.tool', {
+						itemIndex,
+					});
+				}
+
+				const toolName = item.json.tool;
+				if (toolName === tool.name) {
+					// Extract the tool name from arguments before passing to MCP
+					const { tool: _, ...toolArguments } = item.json;
+					const schema: JSONSchema7 = tool.inputSchema;
+					// When additionalProperties is not explicitly true, filter to schema-defined properties.
+					// Otherwise, pass all arguments through
+					const sanitizedToolArguments: IDataObject =
+						schema.additionalProperties !== true
+							? pick(toolArguments, Object.keys(schema.properties ?? {}))
+							: toolArguments;
+
+					const params: {
+						name: string;
+						arguments: IDataObject;
+					} = {
+						name: tool.name,
+						arguments: sanitizedToolArguments,
+					};
+					const result = await client.callTool(params, CallToolResultSchema, {
+						timeout: config.timeout,
+					});
+					returnData.push({
+						json: {
+							response: result.content as IDataObject,
+						},
+						pairedItem: {
+							item: itemIndex,
+						},
+					});
+				}
+			}
+		}
+
+		return [returnData];
+	}
+}