Can you filter on a custom field value through the API?

Posted on behalf of a customer. Original posting date 2014-08-20.

Using the LP API is it possible to filter using a custom field value? That is, I want my API call to return all of the projects which have a particular custom field value set.

Something like this:

https://app.liquidplanner.com/api/workspaces/#####/projects?filter[]=custom_field_values contains MP_Type

I imagine the answer is "no", based on the API documentation, but I thought I'd ask anyway.