The regular Matomo HTTP Reporting API is not available within WordPress. Instead we utilise the WordPress REST API.
For more details about each method and all the available parameters please view the HTTP Reporting API reference. The idSite parameter is automatically set within WordPress and you don't need to provide this value. The token_auth is never needed as well since the authentication is done through WordPress.
Example endpoint: https://example.com/index.php?rest_route=/matomo/v1
Example request: https://example.com/index.php?rest_route=/matomo/v1/api/processed_report&period=date&date=year&filter_limit=10&apiModule=Actions&apiActions=getPageUrls
Namespace: matomo/v1
GET api/processed_reportGET api/report_metadataGET api/matomo_versionGET api/metadataGET api/segments_metadataGET api/widget_metadataGET api/row_evolutionGET api/suggested_values_for_segmentGET api/settingsPOST annotations/addPOST annotations/allPOST core_admin_home/invalidate_archived_reportsPOST core_admin_home/run_scheduled_tasksGET dashboard/dashboardsGET image_graph/getGET languages_manager/available_languagesGET languages_manager/available_languages_infoGET languages_manager/available_language_namesGET languages_manager/language_for_userGET live/countersGET live/last_visits_detailsGET live/visitor_profileGET live/most_recent_visitor_idGET visits_summary/visits (requires version 4.0.2 or newer)GET visits_summary/unique_visitors (requires version 4.0.2 or newer)DELETE privacy_manager/data_subjectsGET privacy_manager/export_data_subjectsPOST privacy_manager/anonymize_some_raw_dataGET scheduled_reports/reportsPOST scheduled_reports/send_reportPOST segment_editor/addPUT segment_editor/updateDELETE segment_editor/deleteGET segment_editor/getGET segment_editor/allGET sites_manager/allGET sites_manager/all_sites_idGET users_manager/usersGET users_manager/users_loginGET users_manager/userGET goals/goalsGET goals/goal