Send with confidence.
One idempotency key per request. Retry safely without creating another message, and track it from queued to delivered or failed.
Explore messagingWhatsApp infrastructure, connected.
Your product.
Their WhatsApp.
One API.
Build the connection. We handle the messaging.
A developer-first API and an operations workspace, from the first request to the next conversation.
Invitation-based access. Built by Asas Labs Ltd.
send-message.httpExample request
POST
/api/v1/messages{
"from": "default",
"to": "+15551234567",
"type": "template",
"template": {
"name": "hello_world",
"language": "en_US"
}
}Authorization: Bearer <your_api_key>Idempotency-Key: welcome-001
202 Accepted
{ "status": "queued" }Illustrative delivery
Built around the details that matter
Idempotent sends
Signed webhooks
Tenant isolation
The messaging foundation
Less plumbing.
More possibility.
Bring WhatsApp into your product with the building blocks you need to send, receive, and stay in control.
Keep the conversation moving.
Receive inbound messages and status updates at your endpoint. Signed webhooks, delivery retries, and event replay keep your integration in sync.
Explore webhooksGive every customer their space.
Organization-scoped API keys keep messages, media, and endpoints separated. Provision customer workspaces through the API as your product grows.
Explore provisioningFrom code to conversation
An API for your app.
A workspace for
your team.
Your developers ship the integration. Your team gets a place to follow conversations, manage contacts, and run campaigns.
- Shared inbox with text and media replies
- Contacts, audiences, and consent controls
- Campaign scheduling and delivery visibility
- API keys, templates, and webhook management
C / workspaceIllustrative view
JD
Jamie DoeCustomer conversation
Example conversation
Hi! Can you send me the details?10:42
Of course. Here’s everything you need.10:43
Designed to be understood
Start with the docs.
Build on your terms.
REST endpoints, a public OpenAPI contract, and request examples. Understand the integration before you write the first line.
Read the documentation01
Connect your numberSet up your workspace and WhatsApp channel.
02
Send your first requestUse an organization key and an idempotency key.
03
Listen for the next eventReceive replies and status updates at your endpoint.
https://castapi.dev/api/v1/messagesA few useful answers
Before you build.
Who is CastAPI for?
Developers adding WhatsApp to their software, and the teams managing those conversations. Use the API from your product and the customer portal for day-to-day messaging operations.
How do I get access?
CastAPI currently uses invitation-based onboarding. Request access by email and the Asas Labs team will coordinate your workspace setup. Existing customers can sign in to their workspace. Public self-service signup is not available yet.
Do I need a WhatsApp Business account?
Yes. Sending requires a connected WhatsApp Business Account and an eligible phone number. Meta’s approval, template, consent, and messaging-window requirements still apply.
Can I use just the API?
Yes. Send messages, manage templates and media, register webhooks, and provision organizations through the API. The portal gives your team a place to manage and monitor the same workspace.
Where can I find pricing?
Commercial terms are agreed during onboarding. Public self-service plans and checkout are not available yet. Meta’s messaging charges and policies also apply.
Your next connection starts here