I should probably mention that I use mendeley. It seems to have a bug. MBE citations with URL and the access macro activated have the form
```
Sato S, Tabata S, Hirakawa H, et al. (322 co-authors). 2012. The tomato genome sequence provides
    insights into  fleshy fruit evolution. Nature [Internet] 485:635–641. Available from: http://www.nature.com/
    doifinder/10.1038/nature11119
```
This is quite far from usable. I just saw that the URL is not coming from the URL variable, but from the access macro. Sorry for the confusion. However, the URL variable seems to be set in mendeley (and there is no option to change the behavior).

Next time I'll cross-check it with Zotero or citeproc-node, before making any suggestions.