WhatsApp Message Delivery
Reach people on WhatsApp with approved templates, consent checks, and delivery status.
What it adds
A WhatsApp delivery path that respects the messaging window, uses pre-approved templates, and tracks consent and delivery state.
What your agent is told to do
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What your agent is told to do
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Model the messaging window explicitly. Outside the window only a pre-approved template may be sent; inside it a free-form reply is allowed. Every send must decide which case it is in before it constructs anything.
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Store approved templates and their parameters in the app, with the language variants each one has been approved for, and validate the parameter set against that record before dispatch rather than discovering a mismatch from a rejection.
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Record consent per recipient with a timestamp and the source of that consent, and check it at dispatch time. A recipient who has withdrawn consent must be unreachable on this channel from that moment.
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Send from the app's background-job system and keep a message row with a stable identifier and a delivery state updated only from verified provider callbacks.
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This brief owns WhatsApp only. If the app also has an SMS path, the choice of which channel a given notification uses belongs to the notification routing layer, not to either delivery integration, so the two do not each decide to send.
Edge cases it handles
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Edge cases it handles
8- Sending free-form content when the conversation window has closed will simply be rejected. Determine the window state from the last inbound message before composing, and fall back to the appropriate approved template.
- Consent and channel eligibility are separate questions. A recipient may have consented and still not be reachable on WhatsApp at that number, and both must be checked before the message is queued.
- A template can be edited, re-approved, renamed, or approved in one language and not another. Pin the version and language a message was built against, and fail loudly on a mismatch instead of sending a message with the wrong or missing parameters.
- Delivery callbacks arrive on a public endpoint, can be replayed, and can arrive out of order. Verify their authenticity, apply them idempotently, and never let an older event overwrite a newer state.
- A recipient who cannot be reached on WhatsApp needs a defined fallback — another channel or a visible failure — decided by the routing layer rather than silently dropped by the integration.
- Retries after a timeout must not produce a second conversation-opening message, which is both confusing and separately billable. Use a stable per-message key.
- Template messages are billed by conversation category. Enforce a per-account ceiling so a retry storm cannot run up an unbounded cost.
- When the provider is unavailable, the triggering action must complete, the message must remain queued, and nothing in the app should claim the recipient has been contacted.
Definition of done
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Definition of done
8- Every send resolves the messaging window and chooses a template or free-form path accordingly.
- Templates, their parameters, and approved languages are stored and validated before dispatch.
- Consent is recorded with a timestamp and source and re-checked at dispatch time.
- Delivery callbacks are authenticated, idempotent, and never regress a message to an older state.
- Retries do not open a second conversation or send a duplicate message.
- Unreachable recipients produce a defined outcome handled by the routing layer, not a silent drop.
- The feature matches the existing design system.
- No existing functionality is broken.
Related features
Firebase Cloud Messaging
Firebase Cloud Messaging
Deliver push through Firebase with registration tokens that stay valid as devices change.
What it does
A Firebase-backed push channel with server-side token lifecycle management, consistent payload handling across platforms, and safe handling of the routes a notification opens.
How it works
- 1 Store one record per device registration, tied to the account signed in at the time, the platform it came from, and when it was last confirmed working, and let one account hold many of them.
- 2 Send from the app's existing background-job system with the provider credentials held server-side, and treat every send as a job that can be retried rather than work done inline during a request.
- 3 Decide, per notification type, whether the payload is meant to be displayed by the platform or handled by the app, and keep that decision the same on every platform. The same event behaving as a visible alert on one platform and a silent update on another produces bugs nobody can reproduce.
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/firebase-cloud-messaging
OneSignal Push Notifications
OneSignal Push Notifications
Send push notifications to the right devices, with user preferences respected.
What it does
A push delivery path through OneSignal covering subscription registration, audience targeting, per-channel preferences, and delivery outcomes recorded against the app's own records.
How it works
- 1 Find the events the app already notifies on by email or in-app, and treat push as another channel for those same events rather than a separate notification system with its own triggers.
- 2 Record the link between a push subscription and an account on the server, established at sign-in and severed at sign-out, so a device that changes hands does not keep receiving the previous user's notifications.
- 3 Hold the provider credentials server-side and send every message from the app's existing background-job system, so a slow or failing provider never blocks a web request.
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/onesignal-push-notifications
Postmark Transactional Email
Postmark Transactional Email
Send transactional email through Postmark on the right stream, with bounces tracked.
What it does
A Postmark delivery path that separates message streams, honours suppression, and retains provider identifiers for diagnostics.
How it works
- 1 Put Postmark behind the app's existing mail layer as one adapter, so no calling code constructs a provider-specific payload. This entry is an alternative to the other transactional email integrations, not an addition — pick one adapter and keep the mail layer identical.
- 2 Classify every outbound message as transactional or broadcast and bind that classification to the matching message stream at the mail layer, so the choice is made once and cannot be got wrong at an individual send site.
- 3 Send from the app's background-job system and persist the provider's message identifier on the record the moment it comes back, so a support question about one email can be answered without guessing.
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/postmark-transactional-email
How it works
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Copy the link
Grab the Markdown instruction URL for this feature.
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Give it to your AI
Paste it into Claude Code, Cursor, v0, Lovable — whatever you build with.
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It inspects, then implements
Your agent reads your existing app first, then adds the feature to fit it.
Works with your stack
These instructions are written to adapt. They tell the agent to detect your framework, match your existing design system, and reuse what you already have — rather than assuming a particular stack.
Need it tighter than that? Customize the feature and tell it exactly what you're running.