Custom tools

import { tool, createSdkMcpServer } from "@anthropic-ai/claude-agent-sdk";
import { z } from "zod";

const getOrder = tool(
  "get_order",
  "Look up a customer order by its reference and return status, items and delivery date",
  {
    reference: z.string().describe("Order reference, for example ORD-1042"),
  },
  async ({ reference }) => {
    const res = await fetch(`https://orders.internal.example/api/orders/${encodeURIComponent(reference)}`);
    const order = await res.json();
    return {
      content: [{ type: "text", text: `${order.reference}: ${order.status}, due ${order.delivery_date}, ${order.items.length} items` }],
    };
  },
);

export const shop = createSdkMcpServer({ name: "shop", version: "1.0.0", tools: [getOrder] });

from typing import Annotated, Any
import httpx
from claude_agent_sdk import tool, create_sdk_mcp_server

@tool(
    "get_order",
    "Look up a customer order by its reference and return status, items and delivery date",
    {"reference": Annotated[str, "Order reference, for example ORD-1042"]},
)
async def get_order(args: dict[str, Any]) -> dict[str, Any]:
    async with httpx.AsyncClient() as client:
        r = await client.get(f"https://orders.internal.example/api/orders/{args['reference']}")
        order = r.json()
    return {"content": [{"type": "text",
             "text": f"{order['reference']}: {order['status']}, due {order['delivery_date']}"}]}

shop = create_sdk_mcp_server(name="shop", version="1.0.0", tools=[get_order])

import { query } from "@anthropic-ai/claude-agent-sdk";
import { shop } from "./shop-tools";

for await (const msg of query({
  prompt: "Where is order ORD-1042 and when will it arrive?",
  options: {
    mcpServers: { shop },
    allowedTools: ["mcp__shop__get_order"],
  },
})) {
  if (msg.type === "result" && msg.subtype === "success") console.log(msg.result);
}

opts = ClaudeAgentOptions(mcp_servers={"shop": shop}, allowed_tools=["mcp__shop__get_order"])
async for msg in query(prompt="Where is order ORD-1042 and when will it arrive?", options=opts):
    if isinstance(msg, ResultMessage) and msg.subtype == "success":
        print(msg.result)

const listRecentOrders = tool(
  "list_recent_orders",
  "List a customer's most recent orders",
  {
    customer_id: z.string(),
    limit: z.number().int().min(1).max(50).optional().describe("How many orders to return (default 10)"),
  },
  async ({ customer_id, limit }) => {
    const n = limit ?? 10;
    const orders = await ordersApi.recent(customer_id, n);
    return { content: [{ type: "text", text: orders.map((o) => `${o.reference} ${o.status}`).join("\n") }] };
  },
);

const shop = createSdkMcpServer({ name: "shop", version: "1.0.0", tools: [getOrder, listRecentOrders] });

@tool(
    "list_recent_orders",
    "List a customer's most recent orders",
    {
        "type": "object",
        "properties": {
            "customer_id": {"type": "string"},
            "limit": {"type": "integer", "minimum": 1, "maximum": 50,
                      "description": "How many orders to return (default 10)"},
        },
        "required": ["customer_id"],
    },
)
async def list_recent_orders(args):
    n = args.get("limit", 10)
    ...

tool("get_order", "Look up an order by reference", { reference: z.string() }, handler, {
  annotations: { readOnlyHint: true, openWorldHint: false },
});

from claude_agent_sdk import tool, ToolAnnotations

@tool("get_order", "Look up an order by reference", {"reference": str},
      annotations=ToolAnnotations(readOnlyHint=True))
async def get_order(args): ...

options: {
  mcpServers: { shop },
  tools: [],
  allowedTools: ["mcp__shop__*"],
}

@tool("get_order", "Look up an order by reference", {"reference": str})
async def get_order(args):
    try:
        async with httpx.AsyncClient(timeout=10) as client:
            r = await client.get(f"https://orders.internal.example/api/orders/{args['reference']}")
        if r.status_code == 404:
            return {"content": [{"type": "text",
                     "text": f"No order {args['reference']}. References look like ORD-1234; ask the customer to check."}],
                    "is_error": True}
        r.raise_for_status()
        return {"content": [{"type": "text", "text": r.text}]}
    except httpx.HTTPError as exc:
        return {"content": [{"type": "text", "text": f"Order service unavailable ({exc}). Try again shortly."}],
                "is_error": True}

tool(
  "product_photo",
  "Fetch the catalogue photo for a product SKU",
  { sku: z.string() },
  async ({ sku }) => {
    const res = await fetch(`https://cdn.internal.example/products/${sku}.jpg`);
    const bytes = Buffer.from(await res.arrayBuffer());
    return { content: [{ type: "image", data: bytes.toString("base64"), mimeType: "image/jpeg" }] };
  },
);

return {"content": [{
    "type": "resource",
    "resource": {"uri": "report://returns/2026-09", "mimeType": "text/csv",
                 "text": "sku,returns\nMUG-01,14\nTEE-RED-M,9\n"},
}]}

return {
  content: [{ type: "image", data: chartPng.toString("base64"), mimeType: "image/png" }],
  structuredContent: { metric: "weekly_returns", unit: "items", values: [41, 37, 52, 29] },
};

import { tool, createSdkMcpServer, query } from "@anthropic-ai/claude-agent-sdk";
import { z } from "zod";

const RATES = { standard: 0.2, reduced: 0.05, zero: 0 } as const;

const vat = tool(
  "calculate_vat",
  "Add or remove UK VAT from an amount in pounds",
  {
    rate: z.enum(["standard", "reduced", "zero"]).describe("VAT rate band"),
    direction: z.enum(["add", "remove"]).describe("add VAT to a net amount, or remove it from a gross amount"),
    amount: z.number().describe("Amount in pounds"),
  },
  async ({ rate, direction, amount }) => {
    if (amount < 0) {
      return { content: [{ type: "text", text: "Amount must not be negative." }], isError: true };
    }
    const r = RATES[rate];
    const result = direction === "add" ? amount * (1 + r) : amount / (1 + r);
    return { content: [{ type: "text", text: `£${amount.toFixed(2)} -> £${result.toFixed(2)} (${rate}, ${direction})` }] };
  },
  { annotations: { readOnlyHint: true, openWorldHint: false } },
);

const finance = createSdkMcpServer({ name: "finance", version: "1.0.0", tools: [vat] });

for (const prompt of ["What is £480 plus standard VAT?", "Strip VAT from a £63 invoice for children's car seats"]) {
  try {
    for await (const msg of query({ prompt, options: { mcpServers: { finance }, allowedTools: ["mcp__finance__*"] } })) {
      if (msg.type === "assistant") {
        for (const b of msg.message.content) if (b.type === "tool_use") console.log("[tool]", b.name, b.input);
      } else if (msg.type === "result" && msg.subtype === "success") {
        console.log(msg.result);
      }
    }
  } catch (err) {
    console.error(`Prompt failed: ${err}`);
  }
}