> ## Documentation Index
> Fetch the complete documentation index at: https://aixyz.sh/llms.txt
> Use this file to discover all available pages before exploring further.

# agent.ts

> Define your agent with Vercel AI SDK

The agent definition file. Must export a default `ToolLoopAgent` and optionally `accepts` for payment gating and `capabilities` for A2A agent card configuration.

```typescript title="app/agent.ts" theme={null}
import { openai } from "@ai-sdk/openai";
import { stepCountIs, ToolLoopAgent } from "ai";
import type { Accepts } from "aixyz/accepts";
import type { Capabilities } from "aixyz/app/plugins/a2a";
import weather from "./tools/weather";

export const accepts: Accepts = {
  scheme: "exact",
  price: "$0.005",
};

export const capabilities: Capabilities = {
  streaming: false,
  pushNotifications: false,
};

export default new ToolLoopAgent({
  model: openai("gpt-4o-mini"),
  instructions: "You are a helpful weather assistant.",
  tools: { weather },
  stopWhen: stepCountIs(10),
});
```

## Exports

| Export         | Type            | Required | Description                                                         |
| -------------- | --------------- | -------- | ------------------------------------------------------------------- |
| `default`      | `ToolLoopAgent` | Yes      | The agent instance                                                  |
| `accepts`      | `Accepts`       | No       | Payment config — gates the A2A `/agent` route                       |
| `capabilities` | `Capabilities`  | No       | A2A capabilities — controls streaming and push notification support |

When `accepts` is exported, the `/agent` endpoint requires x402 payment. Without it, the agent is not registered on the A2A endpoint. `accepts` can also be an array of payment entries for [multi-network support](/getting-started/payments#multiple-payment-options).

## Capabilities

The optional `capabilities` export controls the A2A agent card's `capabilities` field and the executor's behavior:

```typescript theme={null}
import type { Capabilities } from "aixyz/app/plugins/a2a";

export const capabilities: Capabilities = {
  streaming: false, // default: true
  pushNotifications: false, // default: false
  stateTransitionHistory: false, // default: undefined
};
```

| Field                    | Type      | Default     | Description                                          |
| ------------------------ | --------- | ----------- | ---------------------------------------------------- |
| `streaming`              | `boolean` | `true`      | Whether the agent streams responses via `textStream` |
| `pushNotifications`      | `boolean` | `false`     | Whether the agent supports push notifications        |
| `stateTransitionHistory` | `boolean` | `undefined` | Whether the agent exposes state transition history   |

When `streaming` is set to `false`, the executor uses `agent.generate()` instead of `agent.stream()`, returning the full response as a single artifact rather than streaming chunks. This is useful for agents backed by models or APIs that don't support streaming.