microsoft/vscode · error · Error

Invalid tool name "${tool.name}": only alphanumeric characte

Error message

Invalid tool name "${tool.name}": only alphanumeric characters, hyphens, and underscores are allowed.

What it means

Error "Invalid tool name "${tool.name}": only alphanumeric characters, hyphens, and underscores are allowed." thrown in microsoft/vscode.

Source

Thrown at extensions/copilot/src/extension/conversation/vscode-node/languageModelAccess.ts:996

						name: message.name,
						toolCalls: message.content
							.filter(part => part instanceof vscode.LanguageModelToolCallPart)
							.map(part => part as vscode.LanguageModelToolCallPart)
							.map(part => ({ function: { name: part.name, arguments: JSON.stringify(part.input) }, id: part.callId, type: 'function' })),
					};
					break;
				default:
					return 0;
			}

			return endpoint.acquireTokenizer().countMessageTokens(raw);
		}
	}

	private validateTools(tools: readonly vscode.LanguageModelChatTool[]): void {
		for (const tool of tools) {
			if (!tool.name.match(/^[\w-]+$/)) {
				throw new Error(`Invalid tool name "${tool.name}": only alphanumeric characters, hyphens, and underscores are allowed.`);
			}
		}
	}

	private async countToolTokens(endpoint: IChatEndpoint, tools: readonly vscode.LanguageModelChatTool[]): Promise<number> {
		return await endpoint.acquireTokenizer().countToolTokens(tools);
	}

	private validateRequest(_messages: Array<vscode.LanguageModelChatMessage | vscode.LanguageModelChatMessage2>): void {
		const lastMessage = _messages.at(-1);
		if (!lastMessage) {
			throw new Error('Invalid request: no messages.');
		}

		_messages.forEach((message, i) => {
			if (message.role === vscode.LanguageModelChatMessageRole.Assistant) {
				// Filter out DataPart since it does not share the same value type and does not have callId, function, etc.
				const filteredContent = message.content.filter(part => part instanceof vscode.LanguageModelDataPart);

View on GitHub (pinned to a94b963a32)

When it happens

Trigger: Thrown at extensions/copilot/src/extension/conversation/vscode-node/languageModelAccess.ts:996 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of microsoft/vscode@a94b963a32 (2026-08-12). Data as JSON: /api/errors/7845da8b4f2e4d43. Report an issue: GitHub.