PBI can be accessed via XMLA endpoint which can be consumed by many old components that previously were used with SSRS + has 'dataset execute query' REST API, so in this meaning PBI can be used as headless BI. Don't know much about Tableau/Qlik API, do they provide API for querying their internal semantic model?
[+] [-] peschu|2 years ago|reply
[+] [-] seektable|2 years ago|reply