A2A protocol 0.3 ships gRPC, signed security cards, and 'server-as-agent' recursive composition; 150+ orgs now back it
Google Cloud Blog·medium signal
The Agent2Agent protocol's 0.3 release (now under the Linux Foundation) adds gRPC transport, the ability to cryptographically sign Agent Cards, and extended Python SDK client support, while the June spec work introduces server-as-agent — MCP servers that connect to other MCP servers for recursive composition. Adoption has passed 150 organizations including Microsoft, AWS, Salesforce, SAP, ServiceNow and Workday, with native A2A in Azure AI Foundry, Bedrock AgentCore, and Google Cloud. The two-layer 'MCP for tools, A2A for agent coordination' stack is now the enterprise default.