We’ve made a breaking change in the APIv4 Monitor API. This API lets you retrieve monitor info and update, clone or delete monitors. The change only applies to API users who are using the PUT method to update existing monitors.
So far, the PUT method was the only way to make changing to a monitor definition via the API. The API team recently decided to start introducing the PATCH method as well. PATCH will be the new method for making partial changes to a monitor definition. Partial changes are useful when you only want to change one setting, or a few settings, without having to provide the entire monitor definition. In contrast, a full change specifies the full monitor definition, including all fields - often by retrieving it first using the GET method.
Until recently, the PUT method would accept both partial and full updates. This is no longer true: when you specify a partial update (i.e. not listing the full monitor definition) using the PUT verb, the request will fail and return a 400 Bad Request. If you are facing this issue, simply change the HTTP verb to PATCH, which will accept your partial update.
If you were already using the GET/PUT scenario (retrieving a monitor definition using GET, making a change in the JSON and sending the entire thing back using PUT), you don’t have to do anything.
For more information, please look at the API Swagger documentation.