I've developed an automatic stock photo keywording tool based on feedback from over 100 photographers around the world. The biggest thing I've learned is that every photographer has their own unique workflow when it comes to keywording, so I designed the tool to meet as many needs as possible.
The most important thing is ease of use. The tool is drag-and-drop to upload photos, and then results are generated while the photographer reviews (and edits - if needed) the keywords, titles, and descriptions. Metadata export is supported for the 13 largest agencies (Shutterstock, Adobe Stock, iStock, etc.)
Additionally, the tool does have multilingual support. Keywords, titles, and descriptions can be generated in one of 16 languages (including Spanish, Portuguese, German, Russian, Chinese, Arabic).
The tool is free to use for the first few photos, but beyond that it is PAID. It costs $ to generate the keywords, titles, and descriptions, so a completely free tool wouldn't have been possible unfortunately
Give it a try if interested:
https://www.phototag.ai/ [nofollow]