n8n-io/n8n · error · NodeOperationError

Tool "${tool}" returned an error

Error message

Tool "${tool}" returned an error

What it means

Error "Tool "${tool}" returned an error" thrown in n8n-io/n8n.

Source

Thrown at packages/@n8n/nodes-langchain/nodes/mcp/McpClient/McpClient.node.ts:271

					const result = (await client.result.callTool(
						{
							name: tool,
							arguments: parameters,
						},
						undefined,
						{
							timeout: options.timeout ? Number(options.timeout) : undefined,
						},
					)) as CallToolResult;

					if (node.typeVersion >= 1.1 && result.isError) {
						const textContent = result.content.find((item) => item.type === 'text');
						const errorMessage =
							textContent && 'text' in textContent
								? textContent.text
								: `Tool "${tool}" returned an error`;
						throw new NodeOperationError(node, errorMessage, { itemIndex });
					}

					let binaryIndex = 0;
					const binary: IBinaryKeyData = {};
					const content: IDataObject[] = [];
					const convertToBinary = options.convertToBinary ?? true;
					for (const contentItem of result.content) {
						if (contentItem.type === 'text') {
							content.push({
								...contentItem,
								text: jsonParse(contentItem.text, { fallbackValue: contentItem.text }),
							});
							continue;
						}

						if (convertToBinary && (contentItem.type === 'image' || contentItem.type === 'audio')) {
							binary[`data_${binaryIndex}`] = await this.helpers.prepareBinaryData(
								Buffer.from(contentItem.data, 'base64'),

View on GitHub (pinned to 5ac6606e81)

When it happens

Trigger: Thrown at packages/@n8n/nodes-langchain/nodes/mcp/McpClient/McpClient.node.ts:271 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of n8n-io/n8n@5ac6606e81 (2026-08-12). Data as JSON: /api/errors/f49a7c63cf6003e0. Report an issue: GitHub.