Meta-verified businessGrostify LLC · 2026

WhatsApp and MCP for your product, without fighting Meta.

Grostify Connect is the infrastructure software vendors and agencies use to connect their customers' WhatsApp accounts in minutes and expose their product to Claude and ChatGPT. Embedded Signup, verified webhooks, OAuth 2.1 and Meta cost at cost, always visible.

See how it works →

THE PIPES

Four pieces everyone builds the same way, built once.

Embedded Signup v4

The customer clicks a button, picks their portfolio in Meta's popup and links their number. No hand-copied tokens, no System Users, no weeks of verification.

Webhooks that never drop a message

HMAC-SHA256 signature validated on every delivery, dedupe by message id, retries and an inspector showing exactly what Meta sent.

MCP server with OAuth 2.1

Your API as curated tools, with server-side aggregation and a context budget per tool. Ready for the Claude connectors directory and ChatGPT apps.

Governance and compliance

Read-only by default, per-channel permissions, consent recorded per contact and an exportable audit trail. Designed so the agent cannot do what it should not.

HOW IT WORKS

From zero to first verified message in under fifteen minutes.

01
Create your account
Email and password. No card. A 30-day trial, the time Meta actually takes.
02
Connect WhatsApp
Meta's official popup. Portfolio, WABA and number stay in your customer's name, under Grostify's app.
03
Receive the event
The first message lands signed on your endpoint. You see it in the inspector with the signature verified.
04
Expose your tools
Publish your product's MCP server with OAuth 2.1 and start receiving users from Claude and ChatGPT.

APP REVIEW READY

What Meta checks is already solved.

Meta's reviewer rejects within 24 hours over a broken link or a webhook that does not answer. Connect ships with everything the form asks for.

Public privacy policy with Grostify LLC details and a technical appendix on messaging.
Data deletion page and a Data Deletion Callback that answers the signed_request.
Webhook endpoint with hub.challenge verification and X-Hub-Signature-256 validation.
Consent recorded per contact, with date, source and message category.
One WABA per customer. Messaging limits are per portfolio and never shared.
Meta cost separated from Grostify's fee, per end customer, always visible.

FOR DEVELOPERS

One endpoint, one signature, zero surprises.

This is what Connect validates before accepting any event from Meta. The same code runs on this site.

Read the docs →

// POST /api/webhooks/whatsapp
const raw = await req.text();
const sig = req.headers.get("x-hub-signature-256") ?? "";
const expected = "sha256=" + createHmac("sha256", APP_SECRET)
  .update(raw).digest("hex");

if (!timingSafeEqual(Buffer.from(sig), Buffer.from(expected))) {
  return new Response("invalid signature", { status: 401 });
}
// dedupe by wamid, enqueue, respond 200 in < 1s

WHO IT IS FOR

Three buyers, the same pipes.

Software vendors

You have hundreds of customers asking for WhatsApp inside your product and a team busy on the core. We provide the control plane, you provide the interface.

Agencies

You manage dozens of accounts and have already lost a number. Health per WABA, validated templates and an escalation path when Meta blocks.

Agent builders

Your agent needs to talk on WhatsApp without learning Graph API or paying per bot message. Typed tools, managed 24-hour window, budget per tenant.

Stop building the same thing again.

Early access for software vendors and agencies. We reply within one business day.

No card. Meta cost separate and at cost.