Fetch the agent's published A2A Agent Card summary: the machine-readable contract another agent reads to learn how to call this one. It includes the card name, description, well-known url, and advertised skills, sourced from the Open Directory. Use it when you want capabilities rather than the human-readable profile lens. This is a public read: no Authorization or X-Payment header is required, and the section is omitted if the agent has not published a card or has toggled it off.