Tools

Tools are explicit host functions that the model can request.

import { createAgent, tool } from "@npm-while1/claude-agent-sdk";
import { z } from "zod/v4";

const calculator = tool(
  "calculator",
  "Evaluate a simple arithmetic expression",
  z.object({
    expr: z.string(),
  }),
  async input => {
    return { content: String(Function(`return ${input.expr}`)()) };
  },
);

const agent = createAgent({
  apiKey: process.env.DEEPSEEK_API_KEY,
  baseURL: "https://api.deepseek.com/anthropic",
  model: "deepseek-v4-flash",
  tools: [calculator],
});

The SDK converts Zod schemas to JSON Schema for the model and parses tool input before calling your handler.

Tool result

type ToolResult = {
  content: string | ContentBlock[];
};

If a tool handler throws, the SDK returns an error tool_result to the model instead of crashing the entire loop.