Returns your current wallet balance, the amount reserved for in-flight sends, and the spendable amount. Requires the balance scope.

Lists the price per SMS segment for each network, optionally filtered by ISO-2 country code. Use it to estimate cost before sending. Requires the balance scope.

Deducts from your wallet balance. Queues an SMS to one or many recipients from an approved sender ID. Cost is reserved from your wallet up front and a campaign reference is returned for tracking. A retry-safe idempotency key is attached automatically. Requires the sms:send scope.

Cursor-paginated list of your messages, newest first. Requires the reports scope.

Returns the delivery status of a single message by its reference (uuid). Requires the reports scope.

Cursor-paginated list of your campaigns, newest first. Requires the reports scope.

Returns a campaign with a delivery-status breakdown, by its reference (uuid) or numeric id. Requires the reports scope.

Deducts from your wallet balance. Generates a one-time passcode and delivers it over SMS, voice or email. The returned reference is the uuid of the message it spawns, so you can track delivery with hellio_get_message. A retry-safe idempotency key is attached automatically. Requires the otp scope.

Checks a code the user entered against the most recent OTP for that destination. Returns verified true/false. Requires the otp scope.

Deducts from your wallet balance. Queues a voice call to one or many recipients. Provide either text (synthesized to speech, with an optional voice) or audio_url (an audio file Hellio fetches). Billed per second of audio per recipient. A retry-safe idempotency key is attached automatically. Requires the voice scope.

Deducts from your wallet balance. Queues a batch of HLR number lookups. Lookups run asynchronously; the response confirms how many numbers were accepted. Requires the lookup scope.

Deducts from your wallet balance. Checks one or more email addresses for deliverability (syntax, MX records, mailbox existence, disposable and role-account detection). Billed per address checked. Requires the email:verify scope.

Lists your registered webhook endpoints. Requires the webhooks scope.

Registers an endpoint to receive delivery receipts. The signing secret is returned once, on creation, so store it. Requires the webhooks scope.

Returns the shared short code, per-network session prices, and per-length monthly extension rentals. Requires the ussd scope.

Reports whether a specific extension code is a valid length, free to rent, and its monthly price. Requires the ussd scope.

Cursor-paginated list of your USSD apps, newest first. Requires the ussd scope.

Creates an app that points the short code at your callback URL. Starts in test mode and returns test_secret and live_secret (shown once). The callback URL must be public. Requires the ussd scope.

Updates an app's name, callback URL, or active state. Requires the ussd scope.

Deletes a USSD app. Requires the ussd scope.

Switches the app to test (sandbox) or live. Going live requires an active purchased extension for the app, otherwise the call returns 402 extension_required. Requires the ussd scope.

Rotates one mode's signing secret. The old secret stops working immediately. Requires the ussd scope.

Cursor-paginated list of your rented extensions, newest first. Requires the ussd scope.

Deducts from your USSD balance (separate from SMS credit and your main wallet). Rents a numeric extension on the shared short code, priced by digit length (shorter is premium). Requires the ussd scope.

Releases a rented extension. Requires the ussd scope.

Cursor-paginated list of your USSD sessions, newest first. Filter with status (active, ended, timeout, failed). Requires the ussd scope.

Returns a single session by its uuid, including developer steps and amount charged. Requires the ussd scope.

Drives a USSD session against one of your own apps in test mode, with no telco, no purchased extension, and no charge. Open with new_session: true and empty input, then repeat with the same session_id and the next input until the reply returns action: end. Requires the ussd scope.