chat-sample/src/toolParticipant.ts

import { renderPrompt } from '@vscode/prompt-tsx';
import * as vscode from 'vscode';
import { ToolCallRound, ToolResultMetadata, ToolUserPrompt } from './toolsPrompt';

export interface TsxToolUserMetadata {
	toolCallsMetadata: ToolCallsMetadata;
}

export interface ToolCallsMetadata {
	toolCallRounds: ToolCallRound[];
	toolCallResults: Record<string, vscode.LanguageModelToolResult>;
}

export function isTsxToolUserMetadata(obj: unknown): obj is TsxToolUserMetadata {
	// If you change the metadata format, you would have to make this stricter or handle old objects in old ChatRequest metadata
	return !!obj &&
		!!(obj as TsxToolUserMetadata).toolCallsMetadata &&
		Array.isArray((obj as TsxToolUserMetadata).toolCallsMetadata.toolCallRounds);
}

export function registerToolUserChatParticipant(context: vscode.ExtensionContext) {
	const handler: vscode.ChatRequestHandler = async (request: vscode.ChatRequest, chatContext: vscode.ChatContext, stream: vscode.ChatResponseStream, token: vscode.CancellationToken) => {
		if (request.command === 'list') {
			stream.markdown(`Available tools: ${vscode.lm.tools.map(tool => tool.name).join(', ')}\n\n`);
			return;
		}

		let model = request.model;
		if (model.vendor === 'copilot' && model.family.startsWith('o1')) {
			// The o1 models do not currently support tools
			const models = await vscode.lm.selectChatModels({
				vendor: 'copilot',
				family: 'gpt-4o'
			});
			model = models[0];
		}

		// Use all tools, or tools with the tags that are relevant.
		const tools = request.command === 'all' ?
			vscode.lm.tools :
			vscode.lm.tools.filter(tool => tool.tags.includes('chat-tools-sample'));
		const options: vscode.LanguageModelChatRequestOptions = {
			justification: 'To make a request to @toolsTSX',
		};

		// Render the initial prompt
		const result = await renderPrompt(
			ToolUserPrompt,
			{
				context: chatContext,
				request,
				toolCallRounds: [],
				toolCallResults: {}
			},
			{ modelMaxPromptTokens: model.maxInputTokens },
			model);
		let messages = result.messages;
		result.references.forEach(ref => {
			if (ref.anchor instanceof vscode.Uri || ref.anchor instanceof vscode.Location) {
				stream.reference(ref.anchor);
			}
		});

		const toolReferences = [...request.toolReferences];
		const accumulatedToolResults: Record<string, vscode.LanguageModelToolResult> = {};
		const toolCallRounds: ToolCallRound[] = [];
		const runWithTools = async (): Promise<void> => {
			// If a toolReference is present, force the model to call that tool
			const requestedTool = toolReferences.shift();
			if (requestedTool) {
				options.toolMode = vscode.LanguageModelChatToolMode.Required;
				options.tools = vscode.lm.tools.filter(tool => tool.name === requestedTool.name);
			} else {
				options.toolMode = undefined;
				options.tools = [...tools];
			}

			// Send the request to the LanguageModelChat
			const response = await model.sendRequest(messages, options, token);

			// Stream text output and collect tool calls from the response
			const toolCalls: vscode.LanguageModelToolCallPart[] = [];
			let responseStr = '';
			for await (const part of response.stream) {
				if (part instanceof vscode.LanguageModelTextPart) {
					stream.markdown(part.value);
					responseStr += part.value;
				} else if (part instanceof vscode.LanguageModelToolCallPart) {
					toolCalls.push(part);
				}
			}

			if (toolCalls.length) {
				// If the model called any tools, then we do another round- render the prompt with those tool calls (rendering the PromptElements will invoke the tools)
				// and include the tool results in the prompt for the next request.
				toolCallRounds.push({
					response: responseStr,
					toolCalls
				});
				const result = (await renderPrompt(
					ToolUserPrompt,
					{
						context: chatContext,
						request,
						toolCallRounds,
						toolCallResults: accumulatedToolResults
					},
					{ modelMaxPromptTokens: model.maxInputTokens },
					model));
				messages = result.messages;
				const toolResultMetadata = result.metadatas.getAll(ToolResultMetadata);
				if (toolResultMetadata?.length) {
					// Cache tool results for later, so they can be incorporated into later prompts without calling the tool again
					toolResultMetadata.forEach(meta => accumulatedToolResults[meta.toolCallId] = meta.result);
				}

				// This loops until the model doesn't want to call any more tools, then the request is done.
				return runWithTools();
			}
		};

		await runWithTools();

		return {
			metadata: {
				// Return tool call metadata so it can be used in prompt history on the next request
				toolCallsMetadata: {
					toolCallResults: accumulatedToolResults,
					toolCallRounds
				}
			} satisfies TsxToolUserMetadata,
		};
	};

	const toolUser = vscode.chat.createChatParticipant('chat-tools-sample.tools', handler);
	toolUser.iconPath = new vscode.ThemeIcon('tools');
	context.subscriptions.push(toolUser);
}