Error handling

Every error response uses a consistent envelope:

{
  "success": false,
  "error": {
    "code": "VALIDATION_ERROR",
    "message": "One or more fields failed validation.",
    "details": { "to": "Must be a valid E.164 phone number." }
  }
}

Successful responses have "success": true and a data key (or data + meta for paginated lists).

Error code reference

Code	HTTP	When it occurs
`MISSING_API_KEY`	401	No Authorization header provided.
`INVALID_API_KEY`	401	API key is invalid or revoked.
`ACCOUNT_SUSPENDED`	403	The account is suspended.
`ACCOUNT_PENDING_KYC`	403	KYC is not yet approved.
`INSUFFICIENT_CREDIT`	402	Balance too low for a usage action.
`VALIDATION_ERROR`	422	One or more fields failed validation. The `details` object maps field names to messages.
`RATE_LIMIT_EXCEEDED`	429	Per-minute rate limit exceeded.
`NUMBER_NOT_FOUND`	404	Number not provisioned to your account.
`NUMBER_UNAVAILABLE`	409	No matching number is available to provision.
`PLAN_LIMIT_REACHED`	409	Plan number limit reached.
`DEVICE_OFFLINE`	409	The device for this number is currently offline.
`CROSS_COUNTRY_CALL_NOT_PERMITTED`	422	Voice destination country differs from the source number's country.
`MESSAGE_NOT_FOUND`	404	SMS message not found.
`CALL_NOT_FOUND`	404	Call session not found.
`CALL_ALREADY_ENDED`	409	Call is not in a hangable state (already ended).
`CALL_NOT_RINGING`	409	Answer attempted on a call that is not ringing.
`WEBHOOK_NOT_FOUND`	404	Webhook not found.
`INVALID_EVENT_TYPE`	422	Unknown webhook event type.