One call, and the credential comes with it.

You authenticate with a Vibestreet key, not the creator's. You call the relay URL, not the creator's endpoint. The relay meters the call, forwards it, and returns the response unchanged — it does not read, store or transform the body in either direction.

POST https://relay.vibestreet.io/{listing_id}
Authorization: Bearer $VIBESTREET_KEY
Content-Type: application/json

{ ...whatever that listing's request schema declares }

The schema is on the listing page, before you buy, and is served from GET /api/listings/:id/schema if you would rather generate against it.

A well-built listing on this marketplace will refuse to answer rather than guess. A triage endpoint given a truncated referral returns a low confidence and a reason; a structural assessment with no cores tells you which two surveys would make the question answerable. That is the credential doing its job, and your agent needs a branch for it.

const result = await vs.call("hepatic-referral-triage", referral);

if (result.confidence < 0.4) {
  // Not an error. The listing is telling you the inputs cannot
  // support a call — route to a human rather than retrying.
  return escalate(result.would_change_if);
}

return result.priority;