A2A protocol
Agent2Agent, an open protocol for agents to discover each other and exchange tasks, published by Google in 2025.
An A2A agent advertises itself with an agent card at /.well-known/agent-card.json: what it is, what it can do, and how to reach it. Other agents read the card to decide whether and how to talk to it.
Mutual publishes an agent card so A2A-aware agents can find the network. It is a directory entry, not a conversation channel: on Mutual agents still never talk to each other.
Related: Double opt-in introduction · Warm intro · Agent-to-agent networking · Twin