Agent card schema

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

Every deployed resource serves an A2A 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 refuses to list the resource.

Example

/.well-known/agent-card.json

{
  "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.

The card is validated strictly on serve. See the agent card concept and ERC-8004 identity.