Kitty

Inspiration

Group orders always end the same way: one person becomes the unpaid dispatcher, allergies get missed, and the bill math takes longer than the meal did. We wanted agents to take over the boring parts — without losing what makes ordering together social.

What it does

Kitty is a shared order page where everyone's own AI agent adds their items and dietary restrictions straight into one live cart via WebMCP tools — no forms, no relaying your order through one exhausted human. The host locks the order in, and Kitty splits the bill automatically.

How we built it

Seven document.modelContext.registerTool() calls — browse_menu, add_item, remove_item, set_dietary_restriction, get_order_summary, split_bill, finalize_order — on a Next.js app on Vercel. Every mutating call is scoped server-side to the calling participant's identity, so an agent can only ever touch its own order. State lives in a lightweight session store, synced to every viewer with plain polling — no infrastructure we didn't need.

Challenges we ran into

Letting several independent agents write to one shared cart safely was the real problem. WebMCP's tool boundaries had to double as both a UX contract and a security boundary — otherwise a confused or malicious agent could overwrite someone else's order or invent a priced item that doesn't exist on the menu.

Accomplishments that we're proud of

Real multi-agent collaboration on one mutable session — not just one agent talking to one app — with guardrails (menu allow-lists, per-participant scoping, host-only finalize) tight enough we'd trust it with an actual office lunch order.

What we learned

WebMCP tools aren't just an API surface — they're a trust boundary. The moment more than one agent can touch the same state, "what should this tool refuse to do" matters as much as "what should it do."

What's next for Kitty

Itemized (not just equal) bill splitting, real restaurant menu imports, and letting a host's agent negotiate directly with a restaurant's own WebMCP tools once more storefronts expose them.

Built With

• cloud
• firebase
• google
• in-memory-session-store
• react
• typescript
• web
• webmcp