A registry that changes at runtime

import { createApp, z } from "@kervan/core"
import { createTestClient } from "@kervan/transport/testing"

const app = createApp({ name: "registry", version: "0.1.0" })
app.tool("add", {
  description: "Adds two numbers.",
  input: z.object({ a: z.number(), b: z.number() }),
  handler: ({ a, b }) => String(a + b),
})

const client = await createTestClient(app)
let notified = 0
client.setNotificationHandler("notifications/tools/list_changed", () => {
  notified++
})
// A 2026-07-28 client asks for change notifications on its subscriptions/listen stream.
await client.listen({ toolsListChanged: true })
const names = async () => (await client.listTools()).tools.map((tool) => tool.name).join(", ")
console.log(`before: ${await names()}`)

// While the client is connected: one tool more, one tool less, announced once.
app.tool("multiply", {
  description: "Multiplies two numbers.",
  input: z.object({ a: z.number(), b: z.number() }),
  handler: ({ a, b }) => String(a * b),
})
app.removeTool("add")
await new Promise((resolve) => setTimeout(resolve, 100))

console.log(`after: ${await names()} (list_changed: ${notified})`)
await client.close()