Tool-Use Patterns

import Anthropic from "@anthropic-ai/sdk";

const client = new Anthropic();

const tools: Anthropic.Tool[] = [
  {
    name: "get_weather",
    description: "Return current temperature in Fahrenheit for a city.",
    input_schema: {
      type: "object",
      properties: { city: { type: "string" } },
      required: ["city"],
    },
  },
];

function executeTool(name: string, input: any): string {
  if (name === "get_weather") {
    // real implementation would call an API
    return `72F and sunny in ${input.city}`;
  }
  throw new Error(`unknown tool ${name}`);
}

export async function runAgent(question: string) {
  const messages: Anthropic.MessageParam[] = [
    { role: "user", content: question },
  ];

  for (let turn = 0; turn < 5; turn++) {
    const res = await client.messages.create({
      model: "claude-opus-4-7",
      max_tokens: 1024,
      tools,
      messages,
    });

    messages.push({ role: "assistant", content: res.content });

    if (res.stop_reason !== "tool_use") {
      const text = res.content.find((b) => b.type === "text");
      return text?.type === "text" ? text.text : "";
    }

    const toolUses = res.content.filter((b) => b.type === "tool_use");
    messages.push({
      role: "user",
      content: toolUses.map((t) => ({
        type: "tool_result" as const,
        tool_use_id: t.id,
        content: executeTool(t.name, t.input),
      })),
    });
  }

  throw new Error("agent exceeded turn budget");
}