AgentCard: A Framework-Neutral Identity and Capability Declaration Format for Agent-to-Agent Communication

This document defines AgentCard, a lightweight JSON data format that enables autonomous software agents to declare their identity, capabilities, communication endpoints, and resource pricing in a framework-neutral manner. AgentCard is designed for agent-to-agent (A2A) communication scenarios where agents built with different frameworks — such as LangChain, CrewAI, AutoGen, or custom implementations — must interoperate without prior coordination. An AgentCard is a pure data schema: it carries no execution logic and imposes no transport requirements. It is analogous to an HTTP response header set — a machine-parseable self-description that any compliant reader can interpret. Key properties of AgentCard include a globally unique ULID-based agent identity, dot-namespaced capability identifiers compatible with OpenAI function-calling and Model Context Protocol (MCP) tool schemas, a physics-grounded energy pricing floor derived from Landauer's principle, and an extensible metadata namespace for framework-specific annotations.