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

# Agent card schema

> The A2A agent card every Utter resource serves, with its full field reference.

Every deployed resource serves an [A2A](https://a2a-protocol.org) agent card at `/.well-known/agent-card.json`. It is a flat card at protocol version `0.3.0` carrying the resource's skills, its x402 payment terms, its ERC-8004 identity, and its health and bond. Validation is strict: `additionalProperties` is `false` at the top level, and `payTo` must equal the `resourceId` or the [marketplace](/reference/marketplace-api) refuses to list the resource.

## Example

```json /.well-known/agent-card.json theme={null}
{
  "protocolVersion": "0.3.0",
  "name": "Return the current UTC time as JSON",
  "description": "Returns the current UTC time as an ISO-8601 string.",
  "url": "https://return-the-current-utc-time-as-json.resources.utter.technology/call",
  "version": "1.0.0",
  "capabilities": { "streaming": false },
  "defaultInputModes": ["application/json"],
  "defaultOutputModes": ["application/json"],
  "skills": [
    {
      "id": "now",
      "name": "Current UTC time",
      "description": "Return the current UTC time.",
      "tags": ["time", "utc"],
      "inputModes": ["application/json"],
      "outputModes": ["application/json"]
    }
  ],
  "x402": {
    "scheme": "utter-escrow",
    "network": "eip155:5042002",
    "chainId": 5042002,
    "asset": "0x3600000000000000000000000000000000000000",
    "escrow": "0x87DDD6df70A5CDb5c161C65bfE15e0F6942DD154",
    "pricing": { "model": "metered", "base": "1000", "perKB": "100", "max": "50000" },
    "payTo": "0x…"
  },
  "cache": { "ttlSeconds": 300 },
  "identity": { "standard": "erc-8004", "chainId": 5042002, "agentId": "42" },
  "health": { "verified": true, "score": 100 },
  "bond": { "posted": "1000000" }
}
```

## Fields

| Field                | Type                   | Description                                    |
| -------------------- | ---------------------- | ---------------------------------------------- |
| `protocolVersion`    | string (const `0.3.0`) | The A2A protocol version.                      |
| `name`               | string                 | Human-readable resource name.                  |
| `description`        | string                 | What the resource does.                        |
| `url`                | string                 | The `POST /call` endpoint URL.                 |
| `version`            | string                 | The resource version.                          |
| `capabilities`       | object                 | `{ streaming }`.                               |
| `defaultInputModes`  | string\[]              | Default request content types.                 |
| `defaultOutputModes` | string\[]              | Default response content types.                |
| `skills`             | object\[]              | One or more skills (see below).                |
| `x402`               | object                 | The payment terms (see below).                 |
| `cache`              | object                 | `{ ttlSeconds }`, the card cache lifetime.     |
| `identity`           | object                 | The ERC-8004 identity (see below).             |
| `health`             | object                 | `{ verified, score }`.                         |
| `bond`               | object                 | `{ posted }`, the bonded amount in base units. |

### skills\[]

| Field         | Type      | Description                      |
| ------------- | --------- | -------------------------------- |
| `id`          | string    | Skill id.                        |
| `name`        | string    | Skill name.                      |
| `description` | string    | What the skill does.             |
| `tags`        | string\[] | Discovery tags.                  |
| `inputModes`  | string\[] | Accepted request content types.  |
| `outputModes` | string\[] | Produced response content types. |

### x402

| Field     | Type                          | Description                                                                      |
| --------- | ----------------------------- | -------------------------------------------------------------------------------- |
| `scheme`  | string (const `utter-escrow`) | The gated metered scheme.                                                        |
| `network` | string                        | `eip155:5042002`.                                                                |
| `chainId` | number                        | `5042002`.                                                                       |
| `asset`   | string                        | The USDC token address.                                                          |
| `escrow`  | string                        | The PaymentEscrow address.                                                       |
| `pricing` | object                        | `{ model, base, perKB, max }`.                                                   |
| `payTo`   | string                        | The `resourceId`. Must equal the resource id or the marketplace refuses to list. |

### identity

| Field      | Type                | Description                      |
| ---------- | ------------------- | -------------------------------- |
| `standard` | string (`erc-8004`) | The identity standard.           |
| `chainId`  | number              | The chain the identity lives on. |
| `agentId`  | string              | The ERC-8004 agent id.           |

<Note>
  The card is validated strictly on serve. See [the agent card concept](/concepts/agent-card) and [ERC-8004 identity](/concepts/erc8004-identity).
</Note>