n8n-io/n8n · error · OperationalError

Tool not found

Error message

Tool not found

What it means

Error "Tool not found" thrown in n8n-io/n8n.

Source

Thrown at packages/@n8n/nodes-langchain/nodes/mcp/McpTrigger/McpServer.ts:638

			}

			const callId = extra.requestId ? `${extra.sessionId}_${extra.requestId}` : extra.sessionId;

			try {
				if (!request.params?.name || !request.params?.arguments) {
					throw new OperationalError('Require a name and arguments for the tool call');
				}

				const toolName = request.params.name;
				const toolArguments =
					typeof request.params.arguments === 'object' && request.params.arguments !== null
						? request.params.arguments
						: {};

				const tools = this.sessionManager.getTools(extra.sessionId) ?? [];
				const requestedTool = tools.find((tool) => tool.name === toolName);
				if (!requestedTool) {
					throw new OperationalError('Tool not found');
				}

				// Eager pre-execution credential gate: if the caller has not connected a
				// required private credential, surface the actionable connection URLs
				// (via elicitation when supported, otherwise as text) instead of
				// executing (or enqueuing) the workflow.
				const gateResult = this.pendingGateResults[callId];
				if (gateResult && !gateResult.readyToExecute) {
					return await this.handleCredentialGate(server, gateResult, callId);
				}

				try {
					if (this.executionCoordinator.isQueueMode()) {
						const requestId = extra.requestId?.toString() ?? '';
						this.storePendingResponse(extra.sessionId, requestId);

						// Resolve handlePostMessage so webhook can return and enqueue execution.
						// The handler continues running asynchronously, waiting for worker response.

View on GitHub (pinned to 5ac6606e81)

When it happens

Trigger: Thrown at packages/@n8n/nodes-langchain/nodes/mcp/McpTrigger/McpServer.ts:638 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/970cf1d7e0135534. Report an issue: GitHub.