event_type_not_subscribable

Event type is poll-only. Answered with 400.

What it means

The subscription names an Org-level Event. Those belong to no Identity, and Webhooks are delivered per Identity, so the Webhook could never fire – which is why the registration is refused rather than accepted and then silent.

What to do

Read the type from GET /api/events instead; the refusal names it.

The body

{
  "type": "https://tigby.eu/problems/event_type_not_subscribable",
  "title": "Event type is poll-only",
  "status": 400,
  "detail": "…what was refused, naming this request's own values",
  "code": "event_type_not_subscribable",
  "doc_url": "https://docs.tigby.eu/errors/event_type_not_subscribable",
  "agent_hint": "…the next step, for software"
}

Branch on code. The detail names this request's own Handle, id or limit and is not part of the contract.