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Agent-to-Agent (A2A) Protocol

Agent-to-Agent (A2A) Protocol

1
posts
2026

This post introduces the Agent-to-Agent (A2A) protocol, an open standard for communication between independent agents. It details the core primitives (Agent Card, Task, Message, Part, Artifact) and explains that A2A is a wire protocol, not an agent framework or a tool-calling protocol. The primary use case for A2A is when independently deployed agents, especially those owned by different teams or vendors, need a shared communication contract. The post emphasizes that A2A is not necessary for agents within a single trust boundary, where orchestration frameworks suffice. It highlights the importance of explicit identity and authorization at trust boundaries for security, detailing A2A's transport-layer security model, mandatory HTTPS, and reliance on external identity providers for authentication and authorization. The post also touches on the challenges of delegated permissions and the ongoing development of related standards like identity chaining and delegated-scope rules. It notes that while A2A has reported production use, its prevalence is still unclear due to architectural complexities and the need for robust delegation mechanisms.

2026

When Does the A2A Protocol Actually Matter?

8/4/2026

Introduces the Agent-to-Agent (A2A) protocol, defining its primitives (Agent Card, Task, Message, Part, Artifact) and its role as a framework-agnostic wire protocol for inter-agent communication. It establishes the core decision criteria for adopting A2A: whether agents cross genuine ownership or trust boundaries. The post details A2A's security model, emphasizing transport-layer security, external authentication/authorization, and the Agent Card's role in declaring supported schemes. It discusses the challenges of delegated permissions and the reliance on external identity providers and OAuth for managing reduced-scope access. The post also contrasts A2A with the Model Context Protocol (MCP) regarding authorization and touches on the current state of A2A adoption and its architectural implications.