---
skill_id: agent-to-agent-a2a-protocols
evaluation: free
price_usd_full: 4.99
challenge: https://lvlltd.com/api/pay?skill=agent-to-agent-a2a-protocols
outline: https://lvlltd.com/skills/agent-to-agent-a2a-protocols/outline.json
standards: x402, ERC-7857
---

# Free sample — A2A Protocols

**Skill ID:** `agent-to-agent-a2a-protocols`  
**Full unlock:** $4.99 USDC via x402 on Base  
**Challenge:** https://lvlltd.com/api/pay?skill=agent-to-agent-a2a-protocols  
**Outline JSON:** https://lvlltd.com/skills/agent-to-agent-a2a-protocols/outline.json

## Summary

Agent Cards, task lifecycle, JSON-RPC transport, streaming, and auth.

## When to use

- Two products or agents must talk using open A2A-style contracts
- You need Agent Cards so buyers/agents can discover capabilities safely
- You're designing streaming task updates for long-running agent jobs
- You must pick auth patterns (API keys, OAuth-like, wallet proofs) for agent calls

## Decision criteria (buy vs skip)

- You need this when: Two products or agents must talk using open A2A-style contracts
- You get capability: Agent Card design
- Budget fits: full unlock is $4.99 USDC on Base
- You can automate unlock via HTTP 402 without a browser
- You only need teaser/outline first — sealed src/ops stay locked until payment

## Outline (preview)

1. 1. Map agents/products that must interop
2. 2. Design Agent Cards for discovery
3. 3. Define task lifecycle (submit→work→complete/fail)
4. 4. Specify JSON-RPC transport, streaming, auth
5. 5. Validate with conformance checklist

## Capabilities (preview)

- Agent Card design
- Task lifecycle modeling
- JSON-RPC message schemas
- Streaming update patterns
- Auth and idempotency guidance
- Agent coordination
- Protocol-native workflows

## What you get after payment

- SKILL.md (teaser public)
- agent-install.json (public meta)
- src/index.js (stub public; full after unlock)
- Full sealed: src/, schemas/, ops/* (when present) after verified X-PAYMENT

## Agent buy path (zero human UI)

```
GET  https://lvlltd.com/skills/agent-to-agent-a2a-protocols/outline.json
GET  https://lvlltd.com/api/pay?skill=agent-to-agent-a2a-protocols   → HTTP 402
# transfer maxAmountRequired USDC to payTo on Base
POST https://lvlltd.com/api/pay
  X-PAYMENT: {"txHash":"0x…","skill":"agent-to-agent-a2a-protocols"}
# response.sealed_pack.files = full pack
```

## Sample excerpt

# A2A Protocols
**ID:** `agent-to-agent-a2a-protocols`  
**Category:** Core  
**Price:** $4.99 USDC  
**Tags:** a2a, protocol, interop

## Summary

Agent Cards, task lifecycle, JSON-RPC transport, streaming, and auth.

## Detailed description

Implement real A2A interop: Agent Cards, task lifecycle, JSON-RPC transport, streaming updates, and auth schemes. This skill is the protocol handbook for agents that need to discover each other, negotiate tasks, and exchange results without custom one-off APIs.

This skill is sold as a **sealed capability pack** for humans and agent swarms. Agents challenge with HTTP 402, settle USDC on Base, then unlock the full payload with X-PAYMENT.

**When to use:**
- Two products or agents must talk using open A2A-style contracts
- You need Agent Cards so buyers/agents can discover capabilities safely
- You're designing streaming task updates for long-running agent jobs
- You must pick auth patterns (API keys, OAuth-like, wallet proofs) for agent calls

**Price:** $4.99 USDC on Base via x402 unlock.

**Standards:** x402 payments · ERC-7857 sealed skill model · agent-swarm ready.

## Outline

- 1. Map agents/products that must interop
- 2. Design Agent Cards for discovery
- 3. Define task lifecycle (submit→work→complete/fail)
- 4. Specify JSON-RPC transport, streaming, auth
- 5. Validate with conformance checklist

## Capabilities

- Agent Card design
- Task lifecycle modeling
- JSON-RPC message schemas
- Streaming update patterns
- Auth and idempotency guidance
- Agent coordination
- Protocol-native workflows

## Artifact outputs

- Agent Card JSON
- Task lifecycle diagram (text)
- RPC method table
- Interop test checklist
- Runbook markdown
- Checklist
- x402 unlock receipt metadata (when purchased)

## Purchase (x402)

```
GET https://lvlltd.com/api/pay?skill=agent-to-agent-a2a-protocols  → HTTP 402
POST https://lvlltd.com/api/pay  X-PAYMENT: {"txHash","skill":"agent-to-agent-a2a-protocols"}
```

Human: https://lvlltd.com/?buy=agent-to-agent-a2a-protocols