metadata for BOEntityDefinition

Is this endpoint working? Returns the metadata for BOEntityDefinition

const options = {method: 'GET', headers: {accept: 'application/json', "RequestVerificationToken": document.getElementById("__RequestVerificationToken").value}};

fetch('/api/metadata/BOEntityDefinition', options)
  .then(response => response.json())
  .then(response => console.log(response))
  .catch(err => console.error(err));

GET request is returning a 501 Not Implemented response status code.