Integrating with Calisero needs no SDK, no special configuration and no approval period. You need an account, an API key and a single HTTP call.
Generate the API key
Open your account, go to API keys and create a new one. The key is shown only once, at creation — copy it straight into a secret manager or your application's environment variables. Never commit it to version control.
Use a separate key per environment: one for production, one for staging, one for local development. If one of them leaks, you revoke it without taking the rest of your systems down.
Send the first message
A single POST to the messages endpoint is enough:
curl -X POST 'https://rest.calisero.ro/api/v1/messages' \
-H 'Accept: application/json' \
-H 'Content-Type: application/json' \
-H 'Authorization: Bearer {token}' \
-d '{
"recipient": "+40712345678",
"body": "Your order has shipped. Tracking: 1234567890.",
"sender": "CALISERO"
}'
The response carries the message id, its initial status and the number of parts it was split into. Keep the id: you use it to query delivery state and to correlate callbacks.
Check the number format
The most common first-integration error is the recipient format. Calisero accepts international E.164 numbers — country prefix, no spaces, no parentheses, no local leading zero. For Romania: +40712345678, not 0712345678.
If you work with user-supplied numbers, normalise them before sending. A phone number parsing library saves a lot of debugging time.
Count characters before sending
A standard SMS holds 160 characters in the GSM-7 alphabet. If the message contains Romanian diacritics or emoji, the encoding switches to UCS-2 and the limit drops to 70 characters per part. A 200-character message with diacritics splits into three parts and is billed as three messages.
The API response tells you exactly how many parts were used, in the parts field. Check it in your tests, not on your invoice.
Test before production
A new account includes €1 test credit. Send test messages to your own number and verify: the text arrives whole, diacritics render correctly, the sender is the one you expect.
From here, the next step is listening to delivery events over webhooks, so you know not just that you sent — but that it arrived.
