---
title: "Expose · Affordances"
description: "Nothing reaches agents until an action says who may call it. expose is public, session, or confirm."
url: "https://affordances.vercel.app/docs/concepts/expose"
image: "https://affordances.vercel.app/og/docs/concepts/expose"
lang: "en"
---

# Expose

Nothing reaches agents until an action says who may call it. expose is public, session, or confirm.

`expose` decides whether an action is part of the protocol and who may call it. Without it, an action is an ordinary server action: it doesn't appear in graphs, the handler answers `not_found` for it, and `defineAction` warns in development.

| `expose`  | Who may call it                                                                     |
| --------- | ----------------------------------------------------------------------------------- |
| `public`  | Anyone                                                                              |
| `session` | A caller with a session, by cookie or bearer token                                  |
| `confirm` | A caller with a session, and only with `confirm: true` after the person approved it |

## Sessions

A session is whatever your `auth` resolver returns for a request. Define it once with `createAffordances`, and both the UI path and the agent path use it:

```ts title="lib/affordances.ts"
import { createAffordances } from '@affordances/next'
import { sessionFrom } from '@/lib/auth'

export const { defineAction, defineState } = createAffordances({
  auth: (request) => sessionFrom(request),
})
```

The resolver gets a `Request`. For agent calls, it's the real request, with its cookies and `Authorization` header. For server actions called from your UI, `@affordances/next` builds one from `headers()`.

Actions that need a session are still listed for callers without one, as `available: false` with the reason `Requires a session`. Calling one answers `unauthorized`.

## Confirm

Use `confirm` for anything a person should approve: placing an order, sending a message, deleting data. The first call doesn't run anything. It answers `confirm_required` with a summary:

```json
{
  "ok": false,
  "error": {
    "code": "confirm_required",
    "message": "Order 2 items for $96.00. Resend with confirm: true once the user approves."
  }
}
```

The summary comes from the action's `summary` option, and the agent should show it to the person before resending the same call with `"confirm": true`. `@affordances/react` does this for WebMCP tools, with `window.confirm` unless you pass your own `confirm`. `@affordances/mcp` tells the model to do the same.

```ts
export const placeOrder = defineAction({
  name: 'placeOrder',
  description: 'Place the order for everything in the cart',
  input: z.object({}),
  state: checkout,
  expose: 'confirm',
  guard: ({ state }) => state.cart.count > 0 || 'Your cart is empty',
  summary: ({ state }) => `Order ${state.cart.count} items for ${format(state.cart.total)}`,
  run: (_, ctx) => orders.place(ctx.session!.id),
})
```

`confirm` is a protocol rule, not a promise about the agent. A client can send `confirm: true` without asking anyone. It stops agents from running consequential actions by accident; it doesn't replace authorization.