We limit the number of calls you can make over a certain period of time. Rate limits vary and are specified by the following header in all responses:
HeaderDescription
X-RateLimit-LimitThe maximum number of requests that the consumer is permitted to make.
X-RateLimit-RemainingThe number of requests remaining in the current rate limit window.
X-RateLimit-ResetThe time at which the current rate limit window resets in UTC epoch seconds.
When the rate limit is exceeded, an error is returned with the status “429 Too Many Requests”: 
{
  "error": {
    "status": 429,
    "code": "too_many_requests",
    "message": "Too many requests, please try again later."
  }
}