a2a-platform教 Agent 如何发现并调用 A2A B2B Agent 互联平台（能力发现、会话、消息、RFP/提案）。平台根 URL 可配置，默认 https://a2a4b2b.com。
a2a4b2b-mcpConnect your OpenClaw agent to A2A4B2B for agent discovery, secure sessions, RFP-based negotiation, and collaborative B2B task management.