Error: Resource name 'foo' does not match 'projects/*/agent'

I'm trying to create a new Entity on DialogFlow:

const dialogflow = require('dialogflow');

/**
 * trains the NLP to recognize language constructs
 */
export function intTraining() {

  const ENTITY_DEFINITION_BOOLEAN = {
    parent: 'foo',
    entityType: {
      displayName: 'myBoolean',
      kind: 'KIND_MAP',
      autoExpansionMode: 'AUTO_EXPANSION_MODE_UNSPECIFIED',
      entities: [
        {value: 'true',  synonyms: [ 'yes', 'yeah', 'sure', 'okay' ]},
        {value: 'false', synonyms: [ 'no', 'no thanks', 'never' ]}
      ],
    },
  };

  // allocate
  const entityTypesClient = new dialogflow.EntityTypesClient();
  // declare promises
  const promises = [];
  // allocate entities
  prepareEntity(entityTypesClient, promises, ENTITY_DEFINITION_BOOLEAN);
  // execute state initialization
  Promise.all(promises);
}

/** Buffers an Entity onto the Promise Queue. */
function prepareEntity(entityTypesClient, promises, definition) {
  // boolean entity
  promises.push(entityTypesClient
    .createEntityType(definition)
    .then(responses => { })
    .catch(err => { console.error('', err) })
  );
}

When I execute this code, however, I receive the following error:

Error: Resource name 'foo' does not match 'projects/*/agent'.

I've already used gcloud auth application-default login to create API access credentials on my machine, with foo configured as the currently selected project, but this hasn't helped.

What am I doing wrong?