Protocol & Terminology Glossary — YIELD.AGENTDIET.DEV — Autonomous B2A, A2A, MCP & x402 Node

Authoritative definitions of autonomous agent protocols, payment rails, and trust standards supported by YIELD.AGENTDIET.DEV — Autonomous B2A, A2A, MCP & x402 Node (https://yield.agentdiet.dev).

Autonomous Payment Protocols

x402 Protocol (v2)

An open HTTP 402 Payment Required standard enabling keyless pay-per-call stablecoin settlement (USDC on Base, Arbitrum, Polygon, Optimism, and Avalanche) using EIP-3009 signed authorizations.

IETF MPP (Machine Payments Protocol)

The IETF draft-ietf-httpapi-payment-00 standard negotiating machine-to-machine charges via WWW-Authenticate: Payment HTTP challenge headers.

L402 Protocol

A cryptographic HTTP 402 authentication and micropayment protocol combining stateless macaroons with SHA-256 payment preimages.

Agent Discovery & Execution Standards

A2A (Agent-to-Agent Protocol v0.3.0)

The Linux Foundation standard publishing an agent card at /.well-known/agent-card.json and accepting JSON-RPC 2.0 message/send tasks at /a2a.

MCP (Model Context Protocol)

Streamable HTTP JSON-RPC 2.0 protocol (/mcp and /.well-known/mcp.json) exposing structured tools, resources, and prompts to LLM clients.

ERC-8004 & TDQS

ERC-8004 provides on-chain EVM agent identity passports and reputation registries; TDQS (Tool Definition Quality Score) grades schema completeness and token efficiency.