Error Codes

All errors use this envelope:

{
  "error": {
    "code": "error_code_string",
    "message": "Human-readable description."
  }
}

HTTP Status	Code	Scenario
`401`	`invalid_api_key`	Missing, invalid, or revoked API key
`402`	`insufficient_credits`	Insufficient credits for job/run creation
`403`	`plan_required`	Your plan does not include the requested capability (API access requires Starter or higher; scheduled runs require a plan that permits scheduling)
`404`	`not_found`	Resource not found or not owned by you
`409`	`job_not_ready`	Job not in `ready` status for run/schedule creation
`409`	`webhook_already_exists`	A second webhook endpoint was requested for the same account
`422`	`invalid_webhook_url`	Webhook target is not a public HTTPS URL
`422`	`validation_error`	Request body validation failed
`429`	`rate_limited`	Rate limit exceeded

404 is returned for resources that belong to another user (never 403) to prevent enumeration. 403 only ever signals a plan entitlement failure, never ownership.
401 is identical whether the key never existed or was revoked.
Webhook endpoints are limited to one per account. Update or delete the existing endpoint instead of creating another one.