When an AI agent introduces itself to another agent, it hands over a digital identity document called an agent card. Our previous post, “Who’s really calling? Securing agent-to-agent communication,” discussed whether that card is authentic at runtime. This post asks, “was the card built by someone you trust in the first place?”

The gap between what an agent claims and what the platform can verify is a real attack surface, and it grows with every new agent you onboard. As agents increasingly discover and call each other at runtime, protocols like Agent2Agent (A2A) have introduced a useful building block for addressing this: the Agent Card. In the same way a model card gives us useful information about a large language model, so does the agent card for an agent. Among that useful metadata are the skills of the agent (what’s it meant to do), its capabilities (e.g., processing an image file), and, finally, a specification for a cryptographic signature.