AgentCard

AgentCard is to A2A what HTTP headers are to the web.

A standardized, machine-parseable declaration of agent identity and capability. Pure data schema. Zero execution logic. Works with any framework.

Schema version: 1.0 · License: Apache 2.0 + CC-BY 4.0 (spec)

---

What is AgentCard?

When HTTP was designed, headers solved a critical bootstrapping problem: how does a server know what format a client accepts before any negotiation happens?

AgentCard solves the same problem for agent-to-agent (A2A) communication:

HTTP Header	AgentCard field
Content-Type	capabilities[].id
Accept	capabilities[].input_schema / output_schema
Authorization	endpoint.auth
Server / User-Agent	name + version
Cache headers	metadata.pacr:* (derived from ledger)

An AgentCard is a pure data document — no network calls, no execution logic. Any framework can parse it. It travels as the Payload (P) inside a PACR record.

---

Quick Start

Minimal valid AgentCard

{
"agent_id": "01HZQK3P8EMXR9V7T5N2W4J6C0",
"name": "My Agent",
"version": "1.0.0",
"capabilities": [
{
"id": "text.generate",
"description": "Generate text given a prompt"
}
],
"endpoint": {
"protocol": "http",
"url": "https://agent.example.com/api"
}
}

Generate an agent_id

agent_id is a ULID encoded as Crockford Base32 (26 chars).

# Python
python3 -c "import uuid; print(str(uuid.uuid4()).replace('-','').upper()[:26])"# Rust (Cargo.toml: ulid = "1.0")# let id = ulid::Ulid::new().to_string();# Node.js
npm install ulid && node -e "const {ulid} = require('ulid'); console.log(ulid())"

---

Schema Reference

Full JSON Schema: schema.json

Top-level fields

Field	Req	Type	Description
agent_id	✓	string	ULID Crockford Base32 26-char — globally unique
name	✓	string	Display name 1–128 chars
version	✓	string	semver 2.0
capabilities	✓	array	≥1 capability
endpoint	✓	object	How to reach this agent
pricing	—	object	Cost model: Joules + optional fiat
metadata	—	object	pacr:* fields derived from ledger

Capability fields

Field	Req	Description
id	✓	Dot-namespaced: text.generate, vision.classify
description	✓	Human-readable description
tags	—	Semantic tags for routing
input_schema	—	JSON Schema for input; null = unstructured
output_schema	—	JSON Schema for output

Endpoint fields

Field	Req	Description
protocol	✓	http · grpc · mcp · ws · custom
url	✓	Endpoint URL
health_check	—	Optional health-check URL
auth	—	Auth config; null = no auth

Pricing fields

Field	Description
joules_per_request	Canonical settlement unit. Min: 2.854×10⁻²¹ J (Landauer floor at 300 K)
latency_ms_p50	p50 latency derived from PACR Ω history
currency	ISO 4217 or token symbol
fiat_per_request	Cost in fiat/token (requires currency)

PACR Metadata

pacr:* fields are derived from the causal ledger by the CSO — not self-declared.

Key	Source	Description
pacr:trust_tier	CSO ρ + count	Verified · Established · Basic · Untrusted · Banned
pacr:rho_ema	CSO	ρ = ΔΦ / Λ (causal return rate EMA)
pacr:substrate_scope	Self-declared	Deployment substrate: "M1-Ultra", "AWS-Graviton", etc.
pacr:substrate_gap	Self-declared	Known validation gaps
pacr:ossification_risk	Computed	high · medium · low — substrate diversity health

---

Agent Discovery

Place your AgentCard at .well-known/agent.json on your domain:

https://your-agent.example.com/.well-known/agent.json

Follows Well-Known URIs RFC 8615.

---

Validators

Rust

use agentcard_validator::validate;let json = std::fs::read_to_string("my-agent.json")?;let errors = validate(&json);if errors.is_empty(){println!("Valid AgentCard");}else{for e in&errors {eprintln!("Error: {e}");}}

Python

importjson, jsonschemaschema=json.load(open("schema.json"))
card=json.load(open("my-agent.json"))
jsonschema.validate(card, schema) # raises ValidationError on failure

Node.js

constAjv=require("ajv/dist/2020");constajv=newAjv();constvalid=ajv.validate(require("./schema.json"),require("./my-agent.json"));if(!valid)console.error(ajv.errors);

---

Examples

File	Agent type
examples/llm-agent.json	Language model
examples/code-review-agent.json	Code review
examples/data-pipeline-agent.json	ETL pipeline

---

Design Invariants

1. Pure data — no execution logic, no RPC, no network calls
2. Zero core dependency — any framework can parse without Aevum Core
3. Append-only schema — existing field semantics never change
4. Metadata is derived — pacr:* from ledger, not self-report
5. Landauer floor — joules_per_request ≥ 2.854×10⁻²¹ J at 300 K

---

Contributing

1. Fork → add validator or example → cargo test → Pull Request
2. Issues and RFC proposals welcome
3. All contributions are under Apache 2.0 + the patent non-reservation in NOTICE

---

License

Code — Apache 2.0

Reference implementation and validators: Apache 2.0 with explicit patent grant (Section 3).

See NOTICE: no patent claims on the AgentCard schema or wire format.

Specification — CC-BY 4.0

SPEC-CAUSAL-TOPOLOGY.md, schema.json, *-SPEC.md files: Creative Commons Attribution 4.0.

Allows incorporation into RFCs, standards documents, third-party protocol stacks — attribution only, no separate agreement needed.

Public Domain Posture

AgentCard aims to be the TCP/IP of AI2AI — owned by no one, usable by everyone. The maintainers commit (recorded in NOTICE and git history):

• No proprietary terms or dual-licensing, ever
• No patent claims on any part of the schema
• No commercial edition with withheld capabilities

Any fork preserving this NOTICE is the authoritative continuation of the project.

---

---

AgentCard

AgentCard 之於 AI2AI，如同 HTTP 標頭之於 Web。

標準化、機器可解析的 Agent 身份與能力聲明。 純數據規格，無執行邏輯，適用於任何框架。

規格版本: 1.0 · 授權: Apache 2.0 + CC-BY 4.0 (spec)

---

什麼是 AgentCard？

HTTP 設計時，標頭解決了一個關鍵的啟動問題：在任何協商發生之前，伺服器如何知道客戶端接受什麼格式？

AgentCard 為 Agent 對 Agent（A2A）通訊解決了同樣的問題：

HTTP 標頭	AgentCard 字段
Content-Type	capabilities[].id
Accept	capabilities[].input_schema / output_schema
Authorization	endpoint.auth
Server / User-Agent	name + version
快取標頭	metadata.pacr:*（帳本衍生，非自報）

AgentCard 是純數據文件——無網路調用，無執行邏輯。 任何框架均可解析。以 PACR 記錄的 Payload（P）字段傳輸。

---

快速開始

最小合法 AgentCard

{
"agent_id": "01HZQK3P8EMXR9V7T5N2W4J6C0",
"name": "My Agent",
"version": "1.0.0",
"capabilities": [
{
"id": "text.generate",
"description": "Generate text given a prompt"
}
],
"endpoint": {
"protocol": "http",
"url": "https://agent.example.com/api"
}
}

生成 agent_id

agent_id 是以 Crockford Base32 編碼的 ULID（26 字符）。

# Python
python3 -c "import uuid; print(str(uuid.uuid4()).replace('-','').upper()[:26])"# Rust (Cargo.toml: ulid = "1.0")# let id = ulid::Ulid::new().to_string();# Node.js
npm install ulid && node -e "const {ulid} = require('ulid'); console.log(ulid())"

---

規格參考

完整 JSON 規格：schema.json

頂層字段

字段	必需	類型	說明
agent_id	✓	string	ULID Crockford Base32 26 字符——全局唯一身份
name	✓	string	顯示名稱 1–128 字符
version	✓	string	semver 2.0
capabilities	✓	array	至少一項能力聲明
endpoint	✓	object	聯繫方式
pricing	—	object	定價：焦耳 + 可選法幣
metadata	—	object	pacr:* 帳本衍生字段

能力字段

字段	必需	說明
id	✓	點分命名空間：text.generate、vision.classify
description	✓	可讀描述
tags	—	語義標籤用於路由
input_schema	—	輸入格式 JSON Schema；null = 非結構化
output_schema	—	輸出格式 JSON Schema

端點字段

字段	必需	說明
protocol	✓	http · grpc · mcp · ws · custom
url	✓	端點地址
health_check	—	可選健康檢查 URL
auth	—	認證配置；null = 無認證

定價字段

字段	說明
joules_per_request	標準結算單位。最小值：2.854×10⁻²¹ J（300 K 時蘭道爾下界）
latency_ms_p50	基於 PACR Ω 歷史的 p50 延遲
currency	ISO 4217 或代幣符號
fiat_per_request	法幣費用（需要 currency）

PACR 元數據

pacr:* 字段由 CSO（因果結算預言機）從帳本衍生，非 Agent 自報。

鍵	來源	說明
pacr:trust_tier	CSO ρ + 計數	Verified · Established · Basic · Untrusted · Banned
pacr:rho_ema	CSO	ρ = ΔΦ / Λ（因果回報率 EMA）
pacr:substrate_scope	自報	部署基質："M1-Ultra"、"AWS-Graviton" 等
pacr:substrate_gap	自報	已知驗證缺口
pacr:ossification_risk	計算	high · medium · low ——基質多樣性健康度

---

Agent 發現

將 AgentCard 放置於域名下的 .well-known/agent.json：

https://your-agent.example.com/.well-known/agent.json

遵循 Well-Known URIs RFC 8615 慣例。

---

驗證器

Rust

use agentcard_validator::validate;let json = std::fs::read_to_string("my-agent.json")?;let errors = validate(&json);if errors.is_empty(){println!("Valid AgentCard");}else{for e in&errors {eprintln!("Error: {e}");}}

Python

importjson, jsonschemaschema=json.load(open("schema.json"))
card=json.load(open("my-agent.json"))
jsonschema.validate(card, schema) # 失敗時拋出 ValidationError

Node.js

constAjv=require("ajv/dist/2020");constajv=newAjv();constvalid=ajv.validate(require("./schema.json"),require("./my-agent.json"));if(!valid)console.error(ajv.errors);

---

範例

文件	Agent 類型
examples/llm-agent.json	語言模型
examples/code-review-agent.json	代碼審查
examples/data-pipeline-agent.json	數據管道

---

設計不變量

1. 純數據 ——無執行邏輯、無 RPC、無網路調用
2. 零核心依賴 ——任何框架可直接解析，無需 Aevum Core
3. 只增規格 ——現有字段語義永不改變
4. 元數據為衍生值 ——pacr:* 來自帳本，非自報
5. 蘭道爾下界 ——joules_per_request ≥ 2.854×10⁻²¹ J（300 K）

---

貢獻

1. Fork → 添加驗證器或範例 → cargo test → Pull Request
2. 歡迎提交 Issue 和 RFC 提案
3. 所有貢獻採用 Apache 2.0 並受 NOTICE 中專利非保留條款約束

---

授權

代碼 — Apache 2.0

參考實現與驗證器：Apache 2.0，含明確專利授權（第三條）。

見 NOTICE：對 AgentCard 規格及線路格式不保留任何專利主張。

規格文件 — CC-BY 4.0

SPEC-CAUSAL-TOPOLOGY.md、schema.json、*-SPEC.md 文件： Creative Commons Attribution 4.0。

允許引入 RFC、標準文件、第三方協議棧——僅需署名，無需另行協議。

公域立場

AgentCard 旨在成為 AI2AI 的 TCP/IP——無人擁有，人人可用。 維護者承諾（記錄於 NOTICE 及 git 歷史）：

• 永不添加專有條款或雙重授權
• 不申請任何規格相關專利
• 不創建功能受限的商業版本

任何保留此 NOTICE 的複刻版本均視為本項目的正統延續。