Capability Advertisement is the mechanism by which an autonomous agent publishes machine-readable metadata describing the skills, tools and interfaces it exposes, allowing other agents or an orchestrator to discover what it can do without prior hard-coded knowledge. It typically takes the form of a structured manifest, such as an agent card, exchanged during a discovery or handshake phase. It underpins dynamic task routing in multi-agent systems built on protocols such as the Agent Communication Protocol and Agent-to-Agent Protocol.