Voice AI Patient-Intake Agent · Zohaib Ali Mughal

The Brief

Registration by phone, with no half-saved records.

Callers give their details to a voice agent instead of a form. The hard parts are accuracy and safety: names spelled right, invalid dates caught, and no duplicate or half-written patient when a call drops or the network stalls.

Names spelled and confirmed letter by letter; numbers read back once as they are given

Dates, phone numbers, states and ZIP codes validated twice: Zod in the API, CHECK constraints in Postgres

Returning callers found by phone number and offered an update instead of a duplicate

Mock appointment booking from open slots; a slot can only be booked once

English and Spanish; transcripts and summaries stored per call and linked to the patient

Architecture & Stack

One validation contract for the agent, the API and the database.

Caller

U.S. phone numberPSTN

Voice

Retell AITelephony · speech-to-text

LLM agent14-section prompt · 5 tools

ElevenLabsText-to-speech

API

Signed webhooksHMAC check on the raw body

Fastify + ZodTool handlers · REST routes

Data

PostgreSQLDrizzle · patients, calls, appointments

Dashboard

Next.jsServer components, no keys in the browser

Stack

Voice

Retell AIOpenAI modelElevenLabs

Backend

Fastify 5Zod 4Drizzle ORM

Data

PostgreSQL

Frontend

Next.js 16Tailwind 4

Quality

VitestPGlite

Hosting

RailwayVercelDocker

Key Decisions

01The model changes state only through five tools, and every tool validates with the same Zod schemas as the REST API

02Nothing is written before a confirmed read-back, and write tools never retry, so one confirmation cannot create two records

03Every tool call and call event is signature-checked over the raw body before any handler runs

04Prompt, tool schemas and agent settings live in the repo and are provisioned by an idempotent sync script

05Integration tests run the real migrations on PGlite and pin the model's tool schemas to the API's

Walkthrough

Inside the product.

Screenshots from a local run on fictional demo data.

Patient registry · Next.js dashboard

Patient record with identity, contact, address and insurance

One patient record, as the agent saved it

Call transcript showing name spelling, read-back and booking

Call summary and transcript, linked to the record

Spanish-language call transcript with an emergency contact

Caller switches to Spanish mid-call

Call where the caller corrects a phone digit and types an ID on the keypad

A corrected digit and keypad entry for an ID

Agent & API

register_patient tool definition with max_retry 0

The register tool: no retries, confirmed fields only

System prompt section on confirmation before saving

Prompt rules for read-back and saving

OpenAPI documentation listing patient endpoints and signed webhooks

OpenAPI docs generated from the Zod schemas

5Tool-calling functions

53Passing tests

14Prompt sections

A voice agent that can only touch data through validated tools: invalid input comes back as field-level errors the agent re-asks, and a dropped call leaves nothing behind.

Registration by phone, with no half-saved records.

One validation contract for the agent, the API and the database.

Inside the product.

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