§06 工具调用：把能力拆成工具

import { AIChatAgent } from "@cloudflare/ai-chat";
import { streamText, tool, convertToModelMessages, stepCountIs } from "ai";
import { z } from "zod";

export class ChatAgent extends AIChatAgent {
  async onChatMessage() {
    const workersai = createWorkersAI({ binding: this.env.AI });
    const result = streamText({
      model: workersai("@cf/moonshotai/kimi-k2.7-code"),
      messages: await convertToModelMessages(this.messages),
      tools: {
        getWeather: tool({
          description: "Get weather for a city",
          inputSchema: z.object({ city: z.string() }),
          execute: async ({ city }) => fetchWeather(city), // 服务端执行
        }),
      },
      stopWhen: stepCountIs(5), // 最多 5 步，防止死循环
    });
    return result.toUIMessageStreamResponse();
  }
}

// 服务端：只描述，不实现
tools: {
  getLocation: tool({
    description: "Get the user's location from the browser",
    inputSchema: z.object({}),
    // 没有 execute —— 客户端处理
  });
}

// 客户端：用 onToolCall 补上实现
const { messages, sendMessage } = useAgentChat({
  agent,
  onToolCall: async ({ toolCall, addToolOutput }) => {
    if (toolCall.toolName === "getLocation") {
      const pos = await new Promise((r) => navigator.geolocation.getCurrentPosition(r));
      addToolOutput({ toolCallId: toolCall.toolCallId, output: { lat: pos.coords.latitude } });
    }
  },
});

export class ChatAgent extends AIChatAgent {
  maxPersistedMessages = 200; // 仅限存储，不裁剪发给 LLM 的
}