Errors

{
  "error": {
    "code": "VALIDATION_ERROR",
    "message": "currency must be a 3-letter ISO code",
    "details": {}
  }
}

const res = await fetch(url, options)

if (!res.ok) {
  const body = await res.json().catch(() => ({}))
  const err = body.error
  const code = typeof err === "object" ? err?.code : undefined
  const message = typeof err === "string" ? err : err?.message

  if (res.status === 503 && code === "ASSESS_MAINTENANCE") {
    return yourFailOpenPolicy()
  }
  if (res.status === 504 && code === "ASSESS_TIMEOUT") {
    return retryWithSameIdempotencyKey()
  }
  if (res.status === 429) return retryWithBackoff()

  throw new ClausumError(code, message)
}