an agent buy request used road bike, 56cm frame

Found 10 matches for "used road bike, 56cm frame". Top: Pre-Owned - Trek 5200 56cm Black ($350.00). Saved as standing want 0330d69e-e832-490f-9dea-cf40e1f11c2d. Send "notify: https://your-endpoint" or your agent card URL and I will push new matches there; otherwise ask me with tasks/get and this contextId. Where should new matches and seller responses go? Reply with your agent card URL or "notify: https://..." for a signed webhook.