Tend: Voice-First Care Circle for Alexa+

Ambient, voice-first family care circle for Alexa+, coordinating daily medication logging, routine check-ins, sibling tasks, and spoken briefings without complex smartphone apps.

Comment

Inspiration

Watching families care for an aging parent from a distance opened my eyes to a painful daily dilemma. Adult children worry constantly about whether their parents took their medications or are doing okay, but calling multiple times a day feels like nagging. Meanwhile, aging parents often feel micromanaged and find modern smartphone apps confusing, tiny, and frustrating to navigate.

I asked myself: What if family care coordination required no phone to unlock, no passwords to remember, and no tiny buttons to tap?

Smart displays like the Amazon Echo Show already sit naturally on kitchen counters and bedside tables. When Amazon announced Alexa+ with the Model Context Protocol (MCP), I realized I had the exact platform I needed to build Tend: an ambient, voice-first care circle that lets elders stay independent and gives families peace of mind through natural, everyday conversation.

What It Does

Tend brings the entire family care circle directly into Alexa+:

  • For Aging Parents (like 81-year-old Margaret): Margaret doesn't need to touch a screen. She simply talks to her Echo Show:
    • "Alexa, tell Tend I took my morning pills." — Tend logs her dose in milliseconds and confirms with a warm, reassuring response.
    • "Alexa, tell Tend I'm fine." — Resets the reassurance timer and lets her family know she's up and doing well, without invasive indoor cameras.
  • For Adult Children (like Elena): Elena asks while making her morning coffee:
    • "Alexa, how's Mom doing today?" — Tend speaks an instant, factual briefing summarizing medication adherence, check-in status, open care tasks, and doctor appointments.
  • For Sibling Care Coordination: When an errand comes up, like picking up a prescription refill at CVS, sibling David says:
    • "Alexa, tell Tend to claim the prescription task." — The task is claimed hands-free and immediately syncs across the family board so nobody duplicates effort or makes an extra trip.
  • Echo Show Care Board (ui://tend/care-board): On smart displays, Tend renders an interactive, glanceable Care Board styled with Apple-inspired typography on a pitch-black background.
  • Safety First: Tend never provides medical diagnoses or dosing instructions. When dispatching urgent alerts to the circle via Amazon SNS, Tend enforces a strict verbal confirmation safeguard ("Say confirm to dispatch an urgent alert") so accidental alerts are never broadcast.

How I Built It

I engineered Tend from the ground up as a production-ready TypeScript monorepo using pnpm workspaces:

  • Official Model Context Protocol (MCP) SDK: Integrated the official @modelcontextprotocol/sdk (spec 2025-11-25) using the modern Streamable HTTP transport.
  • 8 Focused Voice Tools: Crafted each tool with a single-sentence description and plain-text spoken responses ($\le 280$ characters, no markdown) tailored specifically for voice delivery.
  • Sub-5ms Deterministic Briefings: I deliberately kept LLMs out of the synchronous voice request path. Spoken briefings are synthesized deterministically from database queries, achieving a local $p95$ latency under $3\text{ ms}$ — well within Alexa+'s 250ms voice budget.
  • Enterprise Security & RFC 9728: Built a dedicated OAuth 2.1 authorization server with mandatory S256 PKCE, RFC 9728 Protected Resource Metadata, and strict bare 401 Unauthorized responses (without WWW-Authenticate headers) required by Alexa+.
  • AWS Cloud Infrastructure (CDK v2):
    • AWS Fargate & ALB: Containerized the MCP server to eliminate serverless cold starts during sudden voice interactions.
    • Amazon DynamoDB Single-Table: High-speed datastore with KMS encryption and Point-in-Time Recovery.
    • Amazon Bedrock (Converse API): Runs asynchronously via an EventBridge schedule and Lambda to analyze 7-day adherence trends without slowing down real-time voice queries.
    • Amazon SNS: Dispatches high-priority SMS alerts for confirmed emergencies.
  • Open Source Conformance Tool (alexa-mcp-check): Authored and published a standalone Apache-2.0 CLI that validates any MCP server against Alexa+ protocol and security standards.
  • Tend Care Console: Built an Apple dark-mode widescreen command center for configuring schedules, inviting family members, exporting records, and testing speech audio.

Challenges I Ran Into

  1. Stateless MCP Transport Lifecycles: In stateless mode (sessionIdGenerator: undefined), @modelcontextprotocol/sdk requires instantiating a fresh WebStandardStreamableHTTPServerTransport for each incoming request; attempting to re-use instances throws a runtime exception. I had to restructure my request pipeline to ensure clean per-request transport lifecycles.
  2. The Alexa+ Bare 401 Requirement: While HTTP standards typically include a WWW-Authenticate header with 401 responses, Alexa+'s account linking flow specifically requires no WWW-Authenticate header on unauthenticated /mcp endpoints. I wrote custom Hono middleware and 12 negative security tests to guarantee strict adherence.
  3. Beating the Voice Latency Budget ($p95 < 250\text{ ms}$): Invoking an LLM in the middle of a live voice interaction can easily introduce 2 to 3 seconds of delay, causing Alexa to time out. I solved this by generating briefings deterministically and moving Amazon Bedrock analysis out-of-band via daily EventBridge cron jobs.

Accomplishments That I'm Proud Of

  • Blazing Fast Response Times: Achieved a verified local $p95$ latency of $2.46\text{ ms}$ over 100 consecutive tool invocations — nearly 100x faster than Alexa's latency limit.
  • 100% Test Coverage: All 34 tests across 7 test suites pass completely green (pnpm verify).
  • Giving Back to the Community: Built and open-sourced alexa-mcp-check under Apache-2.0 so any developer building for Alexa+ can easily test their MCP compliance.
  • Zero-Hallucination Healthcare Architecture: Built an architecture that ensures critical health logs and family records remain 100% factual and deterministic.

What I Learned

  • How to design high-throughput MCP servers using Streamable HTTP and stateless transports.
  • The nuances of RFC 9728 Protected Resource Metadata and OAuth 2.1 resource indicator validation.
  • How to balance natural conversational AI with deterministic, zero-hallucination healthcare safety guardrails.

What's Next for Tend

  • Ambient Sensor Integration: Ingesting motion and door contact events from Ring to automatically log morning activity without requiring Mom to speak at all.
  • Fire TV Care Board: Creating a glanceable living room dashboard for Fire TV so family members can see Mom's status from the couch.
  • FHIR Clinical Interoperability: Enabling families to export adherence logs into standardized HL7/FHIR formats for direct sharing with primary care doctors.

Tracks & Mini Challenges Entered

  1. Primary Track: Alexa+ — Full MCP specification compliance, 8 voice tools, Streamable HTTP, OAuth 2.1 PKCE S256, and multimodal Care Board.
  2. Mini Challenge: AWS Builder — Comprehensive AWS CDK v2 stack (infra/cdk), DynamoDB single-table, AWS Fargate, EventBridge-scheduled Amazon Bedrock insights, and Amazon SNS.
  3. Mini Challenge: Open Source — alexa-mcp-check Apache-2.0 conformance checker CLI.

Built With

Share this project:

Updates

Submission history