Errors

Every non-2xx response is:

{"error":{"code":"<machine_code>","message":"<human description>"}}

Status	Code	Meaning / fix
401	invalid_api_key	Missing, malformed, revoked, or unknown key.
402	insufficient_credits	Wallet can’t cover the call — top up.
403	missing_scope	Read-only key on a write endpoint.
403	api_not_enabled / webhooks_not_enabled	Plan lacks the feature — upgrade.
404	not_found	No such resource in your workspace.
404	transcript_not_available / recording_not_available	Not available for this call.
409	contact_exists	Duplicate phone; response includes existing_id.
409	subscription_limit_reached	Max 5 active webhook subscriptions.
409	subscription_not_active	Test events need an Active subscription.
409	not_cancelable	Only queued call requests can be canceled.
422	validation_error	Missing/invalid fields (message says which).
422	invalid_phone	to (POST /calls) or phone_e164 (opt-outs) must be E.164, e.g. +9198xxxxxxxx. A malformed phone_e164 on POST /contacts returns validation_error instead.
422	invalid_agent / invalid_contact / contact_phone_mismatch	Bad references in POST /calls.
422	recipient_dnd / consent_withdrawn	The number is opted out / consent withdrawn.
422	outside_calling_hours	Outside the permitted calling window — pass schedule_if_outside_hours: true to queue for the next window.
422	invalid_url / no_events / invalid_event_type	Webhook subscription validation.
422	invalid_status / invalid_action	PATCH /webhook-subscriptions/{id} — status may only be active or paused.
429	rate_limited	Too many requests — honor Retry-After.