Using search api on several blogs

Hi,

I'd like to search the last blog article with a certain tag that could come from 2 differents Blogs.

The following call to the API is working exactly as I want using a browser 

http://mycommunity/restapi/vc/search/messages?q=tags:TAG&location=blog-board:BLOG1%OR%BLOG2&sort_by=-topicPostDate&restapi.response_style=view

When I use this call in a endpoint I have an error 500. If I replace %OR% by %20OR%20 I have an error 100

Do you know what operator I should use or how to call the API for this?

Thanks

Eric