n8n-io/n8n · error · NodeOperationError

${errorMessage}

Error message

${errorMessage}

What it means

Generic per-item error wrapper in MCP Client execute: calling the remote tool threw (ZodError messages are prettified; other errors use their message). If continueOnFail is on, the error becomes item output JSON; otherwise it is rethrown as a NodeOperationError for the failing itemIndex.

Solutions

1. Read the embedded message — it is the tool's or schema validation's own error
2. Fix the tool arguments or server-side issue, or enable continue-on-fail to keep processing

When it happens

Trigger: Thrown at packages/@n8n/nodes-langchain/nodes/mcp/McpClient/McpClient.node.ts:333 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/14ae71ae63bc8790. Report an issue: GitHub.

Appendix: source

Thrown at packages/@n8n/nodes-langchain/nodes/mcp/McpClient/McpClient.node.ts:333

				} catch (e) {
					const errorMessage =
						e instanceof ZodError ? prettifyError(e) : e instanceof Error ? e.message : String(e);
					if (this.continueOnFail()) {
						returnData.push({
							json: {
								error: {
									message: errorMessage,
									issues: e instanceof ZodError ? e.issues : undefined,
								},
							},
							pairedItem: {
								item: itemIndex,
							},
						});
						continue;
					}

					throw new NodeOperationError(node, errorMessage, {
						itemIndex,
					});
				}
			}

			return [returnData];
		} finally {
			await client.result.close();
		}
	}
}

View on GitHub (pinned to 5ac6606e81)