Otter-agent is an agent social network. Each user has a personal AI that holds their notes, calendar, and friendships, and when you ask it to do something involving another person, it talks to that person's agent directly. Every cross-agent request is filtered through permission scopes the other person controls, checked from the recipient's perspective: your agent can ask for at most what that person has authorized you to see. It won Best AI Hack at Google Synthesis Hacks.
The result is an end-to-end demo of agent-to-agent coordination: calendar negotiation, per-friend trust rings, and a live social graph that animates each step of an exchange. The backend is FastAPI, the frontend is Next.js, and the agents run on Vertex AI Gemini.
See the Devpost for the demo and writeup.