Book a Repair

So far, the dispatcher has only read data. Now we'll give it a tool that changes the calendar and commits the shop to a repair. We'll start without an approval check so you can see the risk directly.

A model that can book a $65 tune-up can use the same single tool call to book a $180 full overhaul. Because you told it to book repairs, it proceeds without treating the higher price as a reason to pause.

This lesson builds the unguarded tool. The next lesson adds the approval check.

Outcome

The dispatcher books a repair into a real slot, including an expensive one, with no human checkpoint. By design, for now.

Hands-on exercise

Create agent/tools/book_repair.ts. It's a write tool, but the shape is the same defineTool you've used four times now. The catalog helpers in agent/lib/shop.ts do the heavy lifting:

• quoteCents(serviceIds) totals the price of the booked services.
• bookSlot(slotId, summary) marks the slot taken and records what it's for.
• getService and formatUsd turn ids into names and cents into dollars.

The input includes serviceIds (a non-empty array from lookup_service), a slotId from check_availability, and an optional bikeLabel. In execute, resolve the service names, total the quote, commit the slot, and return a confirmation.

Leave out the price check and confirmation step for now. We're building the naive version first on purpose.

Try It

Restart and push it toward the most expensive thing on the menu:

npx eve dev

you › my whole drivetrain is shot and the headset's notchy. just do everything,
book me for Tuesday.

  ⚙ lookup_service  { query: "" }
  ⚙ book_repair  { serviceIds: ["tune-up-full"], slotId: "tue-10", bikeLabel: "the commuter" }
  ↳ { booked: true, when: "Tue 10:00am", services: ["Full Overhaul"], total: "$180.00" }

dispatcher › Done! I've booked the commuter in for a Full Overhaul on Tuesday at
10:00am. That's $180.00. See you then!

The agent committed the shop and the customer to a $180 job in a single tool call. It never asked for confirmation or paused before booking. The same path would have handled a $20 flat repair.

If the booking fails with "slot already taken," pick an open slotId from check_availability (the Wednesday 4pm slot is seeded as already booked). If the agent quotes a total that doesn't match the catalog, check that you're totaling with quoteCents, not adding numbers yourself.

Done-When

• agent/tools/book_repair.ts commits a booking via bookSlot and returns the confirmation.
• Booking a cheap service works end to end.
• Booking the Full Overhaul also goes straight through, with no checkpoint.
• You've seen the agent commit $180 unsupervised, and it bothers you a little.

Solution

import { defineTool } from "eve/tools";
import { z } from "zod";
import { getService, quoteCents, bookSlot, formatUsd } from "../lib/shop.js";
 
export default defineTool({
  description:
    "Book one or more services into an open slot for a customer's bike. " +
    "Returns the confirmation and the total quote.",
  inputSchema: z.object({
    serviceIds: z
      .array(z.string())
      .min(1)
      .describe("Service ids from lookup_service."),
    slotId: z.string().describe("An open slot id from check_availability."),
    bikeLabel: z.string().optional().describe("Which of the customer's bikes this is for."),
  }),
  async execute({ serviceIds, slotId, bikeLabel }) {
    const names = serviceIds.map((id) => getService(id)?.name ?? id);
    const total = quoteCents(serviceIds);
    const summary = `${names.join(" + ")}${bikeLabel ? ` (${bikeLabel})` : ""}`;
    const slot = bookSlot(slotId, summary);
    return {
      booked: true,
      when: slot.label,
      services: names,
      total: formatUsd(total),
    };
  },
});

The tool is useful, but an expensive booking still goes through without review. In the next lesson, one approval field will pause those bookings while leaving cheap ones unchanged.