NextOne - a day-operating MCP add-on for Alexa+

Try it in 3 minutes, no account needed: npm start, then open http://127.0.0.1:3000 (type your own sentence into the box; the page is a simulated Alexa+ host, see below).

Alexa+ track, Build, Ship, Shape: Amazon Developer Hackathon. Zero dependencies, Node 20+.

What it does

• "What should I do now?" returns one block plus two previews, on one card.

• "I'm 40 minutes late" rebuilds the rest of the day. No two blocks share a minute, fixed events (a lecture, a dinner) never move, and anything that no longer fits is marked deferred, never done.

• "I did it" is not recorded. Done needs proof: a photo, a file, a link or a third_party reference (a sensor, device or receipt id).

• State survives across sessions (file store; restart test included).

Related MCP server: time-tracking-google-calendar-mcp

Evidence: where it comes from and what counts

Where evidence comes from: the Alexa+ host model passes evidence: {kind, ref} as an argument of the complete_block tool; the server never reads a camera, an Echo sensor or any device itself. In the simulated host, photo X, file X, link https://... or device|sensor|receipt X in the sentence become the ref; whether a real Echo or app would supply it is not tested here. A valid ref is: kind is one of photo, file, link, third_party and ref is a non-empty string after trimming. The server does not open or verify what the ref points to (isValidEvidence in src/domain/schedule.js).

What is different from what Alexa+ already does

See docs/comparison.md. Short version: Alexa+ reminders can be snoozed and followed up until you say you are done. NextOne re-plans the whole remaining day around fixed events and refuses a spoken "done" without proof.

The metric (one definition, used everywhere)

Overlap minutes after a late event = minutes covered by two or more blocks once the user says "I'm N minutes late" (lower is better). Baseline: the behaviour of a reminder that only moves the late item.

The 1000 seeded days are all generated, but scripts/bench.js skips every day whose first block is a fixed event (nothing to run late on), so 751 are counted; SPEC.md's 1000 is the generated count, this table is the counted one. These numbers are generated into docs/metrics.json; npm run check-docs fails if this README disagrees with it.

Required technology and where it is used

Design rules followed from the Alexa+ MCP design guide: one intent per tool, errors always returned with a next step and no internal ids, one title / at most two fields / one action per card (checked by tests), widget packaged as one self-contained HTML file whose resource URI carries a content hash.

Simulation, stated plainly

This is a simulated Alexa+ experience, which the rules allow: "Alternatively, entrants may submit a simulated Alexa+ experience instead" (https://amazonappdev2026.devpost.com/rules, section 4). No Alexa+ device or account was used. host/ is a small stand-in host: a rule-based intent mapper instead of the Alexa+ model, a sandboxed iframe for the card, and the MCP Apps message bridge. The MCP server behind it is real and answers every JSON-RPC call you see in the page's traffic log. Nothing here ran on an Alexa+ device. All data is synthetic. The host-context device names in the simulator (echo-show-8, echo-show-15) are guesses: the docs I read do not list the real values (see the friction log).

Run and test

npm start        # server + simulated host on http://127.0.0.1:3000
npm test         # unit, property, integration and scenario tests
npm run bench    # regenerate docs/metrics.json
npm run check-docs

Architecture

src/domain (pure rules) <- src/application (use cases, card presenter) <- src/adapters (MCP JSON-RPC) <- src/infrastructure (HTTP, file store). A test fails the build if a layer imports upward. See SPEC.md.

Feedback for the platform teams

Real friction met while building: docs/friction-log.md.

License

MIT, see LICENSE.