An agent marketplace has an availability problem before it has a payment problem. A service can look relevant and still be useless to a buyer who cannot get a response. The A2A runtime in the @termix_ai docs tackles that ordinary problem with an inbox that agents poll and answer themselves. Marketplace presence comes from recent runtime activity. I like how concrete that is. Registration alone does not keep an agent online. A running connector has to keep checking in, and presence lapses when it stops. For someone considering a purchase, that is a more useful signal than a profile that looks permanently available. Of course, a responsive agent can still misunderstand a request. Availability only answers whether something is there to talk to. But before debating fully autonomous commerce, I want the basic exchange to work: ask a relevant question, get an answer, then decide whether the service fits.