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Once Upon YOUR Child MCP server

by darcy0408
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Once Upon YOUR Child — MCP server for Alexa+

A self-hosted Model Context Protocol server that lets a voice agent such as Alexa+ tell personalized, feelings-aware bedtime stories from Once Upon YOUR Child.

The child already has heroes in the app: a name, an age, a comfort item, buddies, fears and strengths. This server exposes those heroes and the app's story engine as MCP tools, so a parent can say:

"Alexa, tell Maya a bedtime story. She's worried about her first swim lesson."

and get a choose-your-own-path story about her hero, calibrated to her age, with choices she answers by voice.

Built for the Alexa+ track of the Amazon Build, Ship, Shape hackathon (2026).

Tools

Tool

What it does

list_heroes

The family's saved heroes, so the agent can ask "which hero tonight?"

start_adventure

Opens a Pick-a-Path story for a hero. Returns speech plus choices phrased for the hero's age.

choose_path

Continues with what the child said: "two", "the cave", "the last one", or their own idea.

tell_bedtime_story

A complete wind-down story sized to N minutes, with the hero's buddies along.

narrate

MP3 narration in the app's child-safe storyteller voices, for hosts that play audio.

list_voices

Available narration voices.

One prompt, bedtime, gives a host a ready-made opening.

Every tool returns text meant to be read aloud verbatim. Alexa+ is the narrator; the app is the author.

Related MCP server: EchoFM Studio

Written for the child's age

The app groups children into bands (Sprout ≤5, Explorer 6–8, Adventurer 9–12, Creator 13–14) and the backend writes each scene for that band: sentence length, vocabulary, story depth and number of choices. This server adapts the spoken frame to match:

Band

Choices asked as

Default path

Ending

Sprout

"Theo, which one? Follow the light, or call softly to it?" (no numbers)

short, 4 scenes

"The end. Sweet dreams, Theo."

Explorer

"What should happen next? One: … Two: … Or tell me your own idea."

medium, 6 scenes

"The end. Sweet dreams, Maya."

Adventurer

numbered, up to three choices, "Or say your own idea."

medium, 7 scenes

"The end. Goodnight, Zara."

Creator

numbered, up to three or four choices

medium, 8 scenes

"The end."

Long choice texts are trimmed to their first clause for the ear (the full text stays in structuredContent), and the model's own trailing nudges ("What will you do next?", a restatement of the choices) are stripped so a child hears the question once. Errors are spoken too: a quota hit becomes "Maya's storybook is resting for tonight."

Run it

cp .env.example .env
npx tsx scripts/setup-parent.ts   # creates a parent account + one hero; paste the printed ids into .env
npm install
npm run dev                       # http://0.0.0.0:3333/mcp  (Streamable HTTP, spec 2025-11-25)
npm run smoke                     # in a second terminal: lists tools over HTTP
npm run check:voice               # offline checks of the read-aloud helpers
npx tsx scripts/personas.ts       # live: one hero per age band through the server (costs model calls)

Production: npm run build && npm start. Railway and similar hosts set PORT.

Auth: backend access tokens live about an hour, so the server keeps itself signed in with the refresh token and, failing that, re-mints the anonymous session by OUYC_CLIENT_ID. Set the client id and the server survives restarts and token expiry on its own.

How it talks to the app

Alexa+  ──MCP (Streamable HTTP)──▶  this server  ──HTTPS──▶  Once Upon YOUR Child backend
                                                          /get-characters
                                                          /generate-interactive-story
                                                          /continue-interactive-story
                                                          /generate-story (bedtime_mode)
                                                          /tts/synthesize

The server carries a bearer token for one parent account. It never bypasses the backend's gates:

  • Story and narration routes sit behind the app's parental-consent check.

  • Age calibration is enforced server-side from the hero's verified age.

  • Free-text choices ("something else") are wrapped as story input, never as instructions.

  • Voice-only mode: include_images: false, so no illustration is generated that nobody will see.

  • Bedtime (linear) stories count against the account's quota (free tier: 3 a day, 5 a month). Adventures do not.

Safety notes for a kids' voice experience

  • The child's name and feelings are sent only to the app's own backend, which already handles them under its privacy policy.

  • The premium ElevenLabs voice is hard-gated off for under-13 accounts by the backend, regardless of what this server asks for.

  • The server keeps only an in-memory map of open story choices; no story content is stored here.

Status

  • 2026-09-24: scaffolded; tool surface and transport verified against the MCP SDK (protocol 2025-11-25).

  • 2026-09-25: full loop verified live against the production backend through the MCP server: list_heroes, a three-scene start_adventure / choose_path run answered with "two" and "the first one", a tell_bedtime_story, and narrate returning an MP3 audio block. See scripts/live.ts.

  • 2026-09-25: age-band walkthrough (scripts/personas.ts) with heroes aged 4, 6, 10 and 13. Added age-aware choice phrasing, clause-trimmed labels, echo/nudge stripping, spoken errors, refresh-token auth, and hero details on bedtime stories.

Demo account setup is in scripts/setup-parent.ts (anonymous session, adult declared age, one hero).

License

MIT

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Maintenance

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