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APP IDEA #27 · API · B2B SAAS

1Lookup — one API for phone, email, and IP verification doing ₹3.3Cr a month

Instead of buying a phone validator from one vendor, an email checker from another, and an IP intelligence service from a third — 1Lookup gives you all three through a single API with one credit system. Sub-300ms response times. ₹3.3Cr last 30 days on TrustMRR. 90% cheaper than legacy verification platforms like Twilio Lookup.

₹3.3Cr
Last 30 days revenue (TrustMRR verified)
<300ms
Response time — faster than Twilio Lookup
4-in-1
Phone + email + IP + domain — one credit, one API
90%
Cheaper than enterprise competitors like Twilio Lookup
01 / HOW IT WORKS

What the app actually does

1Lookup's positioning is consolidation — instead of managing three separate vendor contracts, three API keys, and three billing cycles, developers run all data verification through one endpoint and pay from one credit pool. The breadth-under-one-key pitch is what differentiates it from specialists like Twilio (phone-only) or ZeroBounce (email-only).

1

Developer signs up and gets a single API key

One key. No separate credentials for phone vs. email vs. IP. All lookups are debited from a shared credit pool — simple to track and budget for.

2

A single API call validates the data type they need

Phone: returns whether the number is active, the carrier, line type (mobile/VoIP/landline), fraud risk score, and DNC status. Email: verifies deliverability, catches disposables. IP: detects VPNs, proxies, and risky geolocations.

3

The response arrives in under 300ms with enriched data

Not just a pass/fail — a full structured JSON with fraud score, carrier details, risk flags, and compliance signals. Developers use this to block fraud at signup, scrub marketing lists, or enrich CRM data in real time.

4

Dashboard shows lookup volume, accuracy stats, and credit burn rate

Teams can monitor their API usage, see which validation types are being called most, and get alerted when credits are running low — all without building internal monitoring tooling.

02 / INDIA POTENTIAL

Does this work as an India play

India's B2B outreach and marketing industry is enormous — millions of telemarketers, cold emailers, and WhatsApp marketing agencies all sending at scale. The data quality problem (fake leads, DND violations, disconnected numbers) is massive, and the solutions are either too expensive or not India-specific.

DND
India's TRAI DND (Do Not Disturb) registry has 300M+ registered numbers — Indian telemarketers face steep fines for calling DND numbers, making a real-time DND check API critical and underserved.
WhatsApp
Indian B2B outreach is heavily WhatsApp-first — a validation API that checks whether a number is active on WhatsApp (not just a valid phone number) is a gap 1Lookup and its global competitors don't serve.
₹0.10
Realistic India-priced per-lookup rate vs 1Lookup's ~$0.003 (~₹0.25) — opens Indian SMBs, agencies, and CRM vendors who verify millions of numbers monthly but balk at dollar pricing.
Telecom
BSNL, Airtel, Jio, Vi — Indian carrier data through 1Lookup's global API is often stale or inaccurate for Indian mobile numbers. A locally-sourced Indian carrier database is a defensible technical moat.
03 / THE WEEKEND BUILD

Friday to Sunday, hour by hour

Scoped to phone and email validation only for v1 — skip IP/domain for the first weekend. One API, two validation types, one credit system, with a WhatsApp number check as the India-specific differentiator.

Friday
Evening · 3 hrs
7–8 PM Set up a Next.js project, Supabase for auth/database, and register for access to a phone validation data source (Twilio, NumVerify, or direct TRAI data for Indian numbers).
8–9 PM Build the core phone validation endpoint — input a phone number, return: valid/invalid, line type (mobile/VoIP/landline), carrier name, and a basic risk score.
9–10 PM Build the email validation endpoint — SMTP-level deliverability check, disposable domain detection, and MX record verification.
Saturday
Full day · 7 hrs
Morning Build the single universal credit system — one credit pool per account, deducted on every API call regardless of validation type.
Afternoon Add the India-specific WhatsApp number check — given a mobile number, return whether it's an active WhatsApp account (using WhatsApp Business API or a third-party WABA check service).
Evening Add the TRAI DND registry check for Indian numbers — cross-reference each phone against India's official DND database to flag numbers that should not receive marketing calls/SMS.
Sunday
5 hrs
Morning Build the developer dashboard — API key management, live credit balance, lookup history, usage by endpoint type, and a credit top-up flow.
Afternoon Razorpay integration — credit packs priced in rupees (Rs499 for 5,000 lookups, Rs1,999 for 25,000 lookups, Rs7,499 for 100,000 lookups).
Evening Test the full API loop with real Indian phone numbers and emails, check DND status, confirm WhatsApp check works, record the demo for your first post.
04 / APP STACK

What you're actually building with

Nx

Next.js 14

Frontend + API routes

Developer dashboard and the API routing logic in one framework.

Sb

Supabase

Auth + database

Stores developer accounts, API keys (hashed), credit balances, and lookup logs.

Ph

Phone data source (NumVerify/TRAI)

Phone validation

Real carrier data for Indian and international numbers — Indian carrier freshness is the moat.

Wh

WhatsApp Business API

WhatsApp number check

Verifies whether a given mobile number has an active WhatsApp account — the India-specific killer feature.

Dn

TRAI DND API

DND compliance

Cross-references Indian phone numbers against India's Do Not Disturb registry — mandatory for any Indian marketer calling at scale.

Rz

Razorpay

Payments

Rupee-priced credit packs — pay-as-you-go, no monthly subscription required.

05 / WHERE & HOW TO DEPLOY

Going live

Where: Vercel for the app, Supabase for the database. The data quality of the underlying phone validation source is the entire product — invest time upfront researching which provider has the freshest Indian carrier data before building around it.

Push your project to GitHub, import into Vercel — auto-detects Next.js, no config needed.
Research Indian carrier data sources BEFORE writing code — this determines product quality more than anything else in this build.
Add environment variables: SUPABASE_URL, SUPABASE_KEY, PHONE_API_KEY, WHATSAPP_API_TOKEN, TRAI_DND_KEY, RAZORPAY_KEY.
Deploy — Vercel gives you a live .vercel.app URL in under a minute.
Point a custom domain at it from Vercel domain settings.
06 / MARKETING & REVENUE

Getting paying users

How to market it

  • Post the "sent 10,000 WhatsApp messages to a cold list — 3,200 numbers weren't on WhatsApp at all" hook as a reel — the wasted money is the emotion that sells the tool.
  • Run 3-5 reels/day targeting Indian performance marketers, CRM founders, and cold outreach agencies separately.
  • The TRAI DND check is a compliance hook with genuine fear attached — Indian marketers who've received TRAI fines will pay for a reliable DND check immediately.
  • Reach out directly to Indian CRM vendors (Salesmate India, LeadSquared, Zoho) about embedding the API as a data enrichment feature — B2B API distribution.
  • Free 100 lookups on signup, no card required — developers need to test accuracy against their own real data before committing.

Who pays, and why

  • Indian B2B sales and marketing agencies verifying leads before pushing them into dialers or WhatsApp campaigns — the highest-volume use case.
  • Indian SaaS companies validating user signups in real time to block bots and fake accounts during registration.
  • Indian CRM vendors wanting to add phone/email data quality enrichment as a built-in feature for their customers.
Scenario
Paying users/mo
Revenue/mo
Slow start (pay-as-you-go packs)
500 developers × Rs499 avg/mo
Rs2,49,500/mo
CRM integration + steady reels
5,000 developers × Rs499 avg/mo
Rs24,95,000/mo
3-5 reels/day + one CRM vendor partnership
25,000 developers × Rs499 avg/mo
Rs1,24,75,000/mo
07 / START BUILDING

Paste this into Claude or GPT

This prompt sets up the full build context so the AI scopes, plans, and starts coding the project with you from message one.

BUILD_PROMPT.txt
I want to build a real-time phone and email verification API for the Indian market, inspired by 1Lookup, scoped to ship a working version in a single weekend. Core product: 1. A single API endpoint that accepts a phone number or email and returns a structured JSON response with validation data. 2. Phone validation returns: valid/invalid, line type (mobile/VoIP/landline), carrier name, and a basic fraud risk score. 3. Email validation returns: deliverability (SMTP check), disposable domain flag, and MX record status. 4. India-specific feature: WhatsApp number check — given a mobile number, return whether it has an active WhatsApp account. This is the key differentiator no global competitor focuses on for India. 5. India compliance feature: TRAI DND registry check — flag numbers registered on India's Do Not Disturb registry so marketers avoid costly violations. 6. One universal credit system — a single credit pool per account, deducted on every API call regardless of type. 7. Pricing: rupee-denominated credit packs (Rs499 for 5,000 lookups, Rs1,999 for 25,000, Rs7,499 for 100,000). Free 100 lookups on signup. Stack I want to use: Next.js 14 for the developer dashboard and API routing, Supabase for auth, API key management, credit balances, and lookup logs, a phone validation data source (NumVerify or TRAI-aligned source) for carrier data, WhatsApp Business API for the WhatsApp number check, TRAI DND API for compliance checks, Razorpay for credit pack purchases. Deploy target: Vercel. Help me, step by step, one question at a time: 1. Before code: help me evaluate what phone validation data source to use for the freshest Indian carrier data. This determines product quality. 2. Build the phone validation API endpoint first with carrier lookup and basic risk scoring. 3. Build the email validation endpoint with SMTP and disposable domain checks. 4. Build the universal credit system — deduct on each API call, check balance before processing. 5. Add the WhatsApp number check using WhatsApp Business API. 6. Add the TRAI DND registry check. 7. Build the developer dashboard with API key management, usage logs, and credit top-up. 8. Wire up Razorpay for the credit packs. Keep explanations short and India-context aware — Rs-priced, WhatsApp number validation as a first-class India feature, and TRAI DND compliance as a genuine selling point backed by real regulatory risk. Push me to ship the smallest working version first, then improve it. If I get stuck on anything, tell me directly to ask @buildwithkanhaa for the next step or a fresh app idea.

Build this one this weekend

Send me a screenshot of what you ship — it might be the next reel.

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