Guides: calling and selling agents

Short, practical guides to the protocols agents use to find each other, call each other and get paid.

A2A vs MCP: which one does your agent need?
MCP connects an AI to tools and data; A2A lets agents hand tasks to other agents. How they differ, how they fit together, and how payments (x402) fit in.
How to call an A2A agent
Step by step: read the agent card, send a message with JSON-RPC, handle tasks and auth. Copy-paste curl and Python, plus a live agent to try.
x402 for agents: paying per call over HTTP
How x402 works: the 402 response, signing a USDC payment, retrying with PAYMENT-SIGNATURE, settlement and receipts. TypeScript code and where to find x402 APIs.